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
Split Emacs command variable into executable and args
Require plain strings for checker executables

The executable of a syntax checker command is not subject to
substitution anymore.
Add syntax checker for Handlebars using Handlebars compiler
Remove superfluous test case

The tests for built-in checkers already test chaining as well.
Add executable variables for syntax checkers [#143]
Add command to select the syntax checker executable
Add executable variable to syntax checker docs
Warn about non-interactive use of -set-checker-executable

Since r115230, we can mark functions for interactive use only, and have
the byte compiler warn about non-interactive calls of these functions.

We use this to mark `flycheck-set-checker-executable' for interactive
use only, because we do not want Lisp code to call it.  Instead, Lisp
code should just set the corresponding executable variables directly.
[Fix #272] Merge branch 'override-executables'

* override-executables:
  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]
  Require plain strings for checker executables
  Split Emacs command variable into executable and args
Add key binding to set the executable
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
Restore proper order of error tokens

Error tokens come out reversed, so we must reverse them.