Enable live reload for CSS, JS, and HTML templates; fixes T173

Test Plan:
- install one of the browser extensions: http://feedback.livereload.com/knowledgebase/articles/86242-how-do-i-install-and-use-the-browser-extensions-
- run `grunt watch`
- make a change to a scss file
- make a change to a js file
- make a change to a html template file
- see reloads for each

Reviewers: seth, rjmackay

Reviewed By: rjmackay

Subscribers: eyedol, lkamau

Maniphest Tasks: T173

Differential Revision: https://phabricator.ushahidi.com/D30