jshint linter: add option to ignore specific error messages

*warning: very gross approach*

This commit adds the "lint.jshint.errorstoignore" option to arcconfig,
as an array, so that a user is now able to ignore any specific error
messages he wishes, by listing it there.

i.e. (in .arcconfig):

+---------------------------------------------------------------------+
| "lint.jshint.errorstoignore": [ "Missing space after 'function'." ] |
+---------------------------------------------------------------------+

will ignore the annoying "Missing space after 'function'" warning, which
complains about constructions in the form of "foo = function() {}".

I am not aware of a way to disable that checking, without also disabling
the "indent" option, which seems to be often undesirable.

Likely, the proper way of fixing that specific thing is to be implemented
in jshint itself, but it seemed interesting to have a way to supress an
arbitrary error/warning in arcanist.

Signed-off-by: Sergio Correia <sergio.correia@openbossa.org>
unit: add busterjs test unit engine

This commit adds a simple unit test wrapper for busterjs. There is
no support for coverage yet.

Signed-off-by: Sergio Correia <sergio.correia@openbossa.org>
Merge pull request #1 from qrwteyrutiyoup/mailson-merge

Add a way to ignore specific messages from jsHint and add a BusterJS unit engine