Add syntax checker for Ruby using ruby-lint
Change error patterns of ruby-lint checker more simply
Rename ruby-lint to ruby-rubylint
Change the ruby and jruby syntax checkers to run ruby-rubylint afterwards
Support enh-ruby-mode for ruby-rubylint
Fix test cases related to ruby
Support info error level for ruby-rubylint
Fix test cases for ruby-rubylint

expect error column 0 to be nil
Merge branch 'master' into yasuyk-ruby-lint

* master: (43 commits)
  Add key binding to set the executable
  Warn about non-interactive use of -set-checker-executable
  Add executable variable to syntax checker docs
  Add command to select the syntax checker executable
  Add executable variables for syntax checkers [#143]
  Remove superfluous test case
  Simplify the documentation of argument substitution
  Require plain strings for checker executables
  Split Emacs command variable into executable and args
  Try to clarify chaining
  Update the screenshot
  Bump version in master
  Release 0.15
  Refactor error navigation tests
  Fix mocker requirements
  Remove unused test resources
  Update changelog
  Revert "Run all tests on Travis CI"
  Run all tests on Travis CI
  Expect failures if checkers are missing
  ...

Conflicts:
	test/builtin-checkers-test.el
Fix test case names
Install Ruby headers to build native extensions

Required to install ruby-lint
Update changelog
Remove ruby and ruby-jruby checkers [#250]
Refactor ruby test cases

Use a single test resource to test Rubocop and Rubylint
Merge branch 'master' into yasuyk-ruby-lint

* master:
  Fix test cases
  Fix error sorting stability
  Restore proper order of error tokens
Update credits
[Fix #250] Merge branch 'yasuyk-ruby-lint'

* yasuyk-ruby-lint:
  Update credits
  Refactor ruby test cases
  Remove ruby and ruby-jruby checkers [#250]
  Update changelog
  Install Ruby headers to build native extensions
  Fix test case names
  Fix test cases for ruby-rubylint
  Support info error level for ruby-rubylint
  Fix test cases related to ruby
  Support enh-ruby-mode for ruby-rubylint
  Change the ruby and jruby syntax checkers to run ruby-rubylint afterwards
  Rename ruby-lint to ruby-rubylint
  Change error patterns of ruby-lint checker more simply
  Add syntax checker for Ruby using ruby-lint