Chore(core): add Growl notifications back

Add Growl notifications when the server is up, in dev mode only.
Choir(core): Add Jshint as a Gulp task

Add Jshint as a Gulp task, breaking the build when there are
linting problems.
Create src/ folder, and uses root folder for the release, in order
to be compatible with OpsWorks
Choir(core): add postinstall hook to run Gulp

Add postinstall hook to run Gulp, only way I found to run Gulp on
Amazon OpsWorks.