Added grunt task to create builds with [grunt] command
Revise calculation of nextFetchInterval to prevent throttling
Show message when question watched/unwatched

Also update the watch icon state immediately instead of waiting for the
background script's message to get the final status.
Merge branch 'master' of https://github.com/blunderboy/stackeye
Merge branch 'master' of https://github.com/blunderboy/stackeye