Merge pull request #288 from dcoloma/grunt-changes

Bug 1093929 - Improve grunt tasks and add additional options r=jaoo
(cherry picked from commit 76d82cb8da5424be64688c731910ce6eceb2e3fd)
Merge pull request #312 from dcoloma/grunt-changes-1.1

Bug 1093929 - Improve grunt tasks and add additional options r=jaoo