codeclimate/codeclimate-rubocop

This cop checks for non-nil checks, which are usually redundant.

### Example:

    # bad
    if x != nil
    end

    # good (when not allowing semantic changes)
    # bad (when allowing semantic changes)
    if !x.nil?
    end

    # good (when allowing semantic changes)
    if x
    end

Non-nil checks are allowed if they are the final nodes of predicate.

    # good
    def signed_in?
      !current_user.nil?
    end