bbatsov/rubocop

### New features

* New cop `ExtraSpacing` points out unnecessary spacing in files. ([@blainesch][])
* New cop `EmptyLinesAroundBlockBody` provides same functionality as the EmptyLinesAround(Class|Method|Module)Body but for blocks. ([@jcarbo][])
* New cop `Style/EmptyElse` checks for empty `else`-clauses. ([@Koronen][])
* [#1454](https://github.com/rubocop/rubocop/issues/1454): New `--only-guide-cops` and `AllCops/StyleGuideCopsOnly` options that will only enforce cops that link to a style guide. ([@marxarelli][])

### Changes

* [#801](https://github.com/rubocop/rubocop/issues/801): New style `context_dependent` for `Style/BracesAroundHashParameters` looks at preceding parameter to determine if braces should be used for final parameter. ([@jonas054][])
* [#1427](https://github.com/rubocop/rubocop/issues/1427): Excluding directories on the top level is now done earlier, so that these file trees are not searched, thus saving time when inspecting projects with many excluded files. ([@jonas054][])
* [#1325](https://github.com/rubocop/rubocop/issues/1325): When running with `--auto-correct`, only offenses *that cannot be corrected* will result in a non-zero exit code. ([@jonas054][])
* [#1445](https://github.com/rubocop/rubocop/issues/1445): Allow sprockets directive comments (starting with `#=`) in `Style/LeadingCommentSpace`. ([@bbatsov][])

### Bugs fixed

* Fix `%W[]` auto corrected to `%w(]`. ([@toy][])
* Fix Style/ElseAlignment Cop to find the right parent on def/rescue/else/ensure/end. ([@oneamtu][])
* [#1181](https://github.com/rubocop/rubocop/issues/1181): *(fix again)* `Style/StringLiterals` cop stays away from strings inside interpolated expressions. ([@jonas054][])
* [#1441](https://github.com/rubocop/rubocop/issues/1441): Correct the logic used by `Style/Blocks` and other cops to determine if an auto-correction would alter the meaning of the code. ([@jonas054][])
* [#1449](https://github.com/rubocop/rubocop/issues/1449): Handle the case in `MultilineOperationIndentation` where instances of both correct style and unrecognized (plain wrong) style are detected during an `--auto-gen-config` run. ([@jonas054][])
* [#1456](https://github.com/rubocop/rubocop/pull/1456): Fix autocorrect in `SymbolProc` when there are multiple offenses on the same line. ([@jcarbo][])
* [#1459](https://github.com/rubocop/rubocop/issues/1459): Handle parenthesis around the condition in `--auto-correct` for `NegatedWhile`. ([@jonas054][])
* [#1465](https://github.com/rubocop/rubocop/issues/1465): Fix autocorrect of code like `#$1` in `PerlBackrefs`. ([@bbatsov][])
* Fix autocorrect of code like `#$:` in `SpecialGlobalVars`. ([@bbatsov][])
* [#1466](https://github.com/rubocop/rubocop/issues/1466): Allow leading underscore for unused parameters in `SingleLineBlockParams`. ([@jonas054][])
* [#1470](https://github.com/rubocop/rubocop/issues/1470): Handle `elsif` + `else` in `ElseAlignment`. ([@jonas054][])
* [#1474](https://github.com/rubocop/rubocop/issues/1474): Multiline string with both `<<` and `\` caught by `Style/LineEndConcatenation` cop. ([@katieschilling][])
* [#1485](https://github.com/rubocop/rubocop/issues/1485): Ignore procs in `SymbolProc`. ([@bbatsov][])
* [#1473](https://github.com/rubocop/rubocop/issues/1473): `Style/MultilineOperationIndentation` doesn't recognize assignment to array/hash element. ([@jonas054][])

[@bbatsov]: https://github.com/bbatsov
[@jonas054]: https://github.com/jonas054
[@yujinakayama]: https://github.com/yujinakayama
[@dblock]: https://github.com/dblock
[@nevir]: https://github.com/nevir
[@daviddavis]: https://github.com/daviddavis
[@sds]: https://github.com/sds
[@fancyremarker]: https://github.com/fancyremarker
[@sinisterchipmunk]: https://github.com/sinisterchipmunk
[@vonTronje]: https://github.com/vonTronje
[@agrimm]: https://github.com/agrimm
[@pmenglund]: https://github.com/pmenglund
[@chulkilee]: https://github.com/chulkilee
[@codez]: https://github.com/codez
[@emou]: https://github.com/emou
[@skanev]: http://github.com/skanev
[@claco]: http://github.com/claco
[@rifraf]: http://github.com/rifraf
[@scottmatthewman]: https://github.com/scottmatthewman
[@ma2gedev]: http://github.com/ma2gedev
[@jeremyolliver]: https://github.com/jeremyolliver
[@hannestyden]: https://github.com/hannestyden
[@geniou]: https://github.com/geniou
[@jkogara]: https://github.com/jkogara
[@tmorris-fiksu]: https://github.com/tmorris-fiksu
[@mockdeep]: https://github.com/mockdeep
[@hiroponz]: https://github.com/hiroponz
[@tamird]: https://github.com/tamird
[@fshowalter]: https://github.com/fshowalter
[@cschramm]: https://github.com/cschramm
[@bquorning]: https://github.com/bquorning
[@bcobb]: https://github.com/bcobb
[@irrationalfab]: https://github.com/irrationalfab
[@tommeier]: https://github.com/tommeier
[@sfeldon]: https://github.com/sfeldon
[@biinari]: https://github.com/biinari
[@barunio]: https://github.com/barunio
[@molawson]: https://github.com/molawson
[@wndhydrnt]: https://github.com/wndhydrnt
[@ggilder]: https://github.com/ggilder
[@salbertson]: https://github.com/salbertson
[@camilleldn]: https://github.com/camilleldn
[@mcls]: https://github.com/mcls
[@yous]: https://github.com/yous
[@vrthra]: https://github.com/vrthra
[@SkuliOskarsson]: https://github.com/SkuliOskarsson
[@jspanjers]: https://github.com/jspanjers
[@sch1zo]: https://github.com/sch1zo
[@smangelsdorf]: https://github.com/smangelsdorf
[@mvz]: https://github.com/mvz
[@jfelchner]: https://github.com/jfelchner
[@janraasch]: https://github.com/janraasch
[@jcarbo]: https://github.com/jcarbo
[@oneamtu]: https://github.com/oneamtu
[@toy]: https://github.com/toy
[@Koronen]: https://github.com/Koronen
[@blainesch]: https://github.com/blainesch
[@marxarelli]: https://github.com/marxarelli
[@katieschilling]: https://github.com/katieschilling