Remove old JS placeholders for Chrome
Add makeDev, clean makeChrome tasks
Cleanup gruntfile; add makeFirefox
Replace TOK_VER with actual version (so version task can update properly)
Update version to test versioning tasks
Add versioning tasks
Remove unused scripts
Set correct name on XPI artifact
Remove unused underscore.string and watch
Split copy into browser-specific actions; correct name for amo archive
Use build/ as the output dir