adds regex to grunt and fixes CSS image urls
Merge branch 'master' into grunt

Conflicts:
	geonode/static/gruntfile.js
remove obsolete css/*.png|gif
adds lib/img/spinner.gif to repository
add spinner.gif to gruntfile
Merge pull request #1028 from cspanring/grunt

adds regex to grunt and fixes CSS image urls to use one consistent path (lib/img)
cleanup: removes obsolete bower-installer config
Safely check settings for DEBUG_SETTINGS.
Merge pull request #1029 from cspanring/grunt

cleanup: removes obsolete bower-installer config
Merge pull request #1030 from garnertb/master

Safely check settings for DEBUG_STATIC.