Fix for Rails syntax.

There is now little point in running this checker rather than the plain
ruby one.
Make shell escaping less produce fewer useless quotes.

Function inspired by tpope's vim-dispatch.
Refactor FindInParent from haxe.vim to be a util function
Fix Elixir `mix` detection.

Syntax checker now looks up thorugh its parents to find if it is part
of a mix project.
Mix needs the cwd to be set to the mix file.
Cleanup.
add hss syntax checker
ignore output by default
redirect output to dev null for syntax checking
Cleanup.
Added hss to the list of supported languages.
Minor fixes to the docs.  Document g:syntastic_debug.
Fix a bug related to shell escaping.
More shell escaping bugs.
Errorformat adjustments for podchecker.

Deal with error messages like this:

    *** ERROR: =over on line 7 without closing =back at line EOF in file ...
Merge remote-tracking branch 'upstream/master'