RocketChat/Rocket.Chat

# Changelog

This is a changelog of changes made to the saml package for RocketChat.
The package is originally based on https://github.com/steffow/meteor-accounts-saml .

## 9-Nov-2016 danb@catalyst-au.net

* Only do `logoutWithSaml` if we are doing single logout (ie
  `idpSLORedirectURL` is set).  We get an error if we do
  `logoutWithSaml` and `idpSLORedirectURL` is not set.  This was
  discovered when testing with simplesamlphp.  In this latter case,
  `logoutWithSaml` will try to use the standard saml endpoint to
  request the logout resulting in an error.
* **TODO:** doing the standard `Meteor.logout` doesn't seem to be
  enough when logging out.  If the user logs back into RocketChat from
  the same window, they will be automatically logged back in to
  RocketChat, no credentials required.  If you enable single logout
  (ie set `idpSLORedirectURL`), then `logoutWithSaml` will be called
  and the client should be properly logged out.
* Switch to using `Cookies` for the client when recording the saml
  provider and whether single logout is enabled.  If the client has
  multiple rocketchat tabs or windows, this will ensure they all
  log out properly with the idp - but only when single logout
  (`idpSLORedirectURL`) is enabled.

## 31-Oct-2016 danb@catalyst-au.net

* Attempt at SP-initiated logout (**requires more work**).
  * Added configuration setting for SLO (single logout) redirect url
    to the IDP.
  * A `Session` key is set called `saml_provider`; it is unset at
    logout.  Is there a better way?
  * `Meteor.logout` on the client is overridden so that
    `Meteor.logoutWithSaml` is called if `saml_provider` is set.  This
    isn't great - is there a better way?
  * Tested using simplesamlphp as the idp
    * login in using saml
    * then logout using the normal RocketChat logout
    * after some time, you should see the RocketChat login screen
    * if you try to login again, you will have to login to the idp again
      repeating the previous login flow
  * **TODO:** If a user has 2 independent browser login sessions using
    saml, both will log out, but only the one the user logged out from
    appears to be properly logged out of the idp.
    * this might be because we shouldn't be logging out the second session
      but RocketChat / meteor is doing this.

## 17-Oct-2016

* Fixed signing for redirect to idp.
  * At login time, if the idp is configured to verify the redirect to its login screen, it will
    expect `RelayState` as part of the signature.
    Tested with **simplesamlphp** with `'redirect.validate' => TRUE` in the `sp-remote` metadata file
  * Added `privateKey` - `SAML_Custom_Private_Key`
  * Added `privateCert` - `SAML_Custom_Public_Cert`
  * These input fields should point to locations on the the server eg `/path/to/private/certs/`.
  * `privateKey` is used by RocketChat to sign saml requests.