dev setup for bokehjs,
 - supporting incremental builds
 - coffeescript source maps
 - separate js files, vs a single combined bokehjs file
TODO:
 - extend this to bokehjs demo/test files
 - think about removing all the static files from bokeh/server/static
- fixed template to use bokehjs_file endpoint for serving bokeh.js
- fixed typo, naming boostrap2 vs bootstrap
Merge pull request #227 from ContinuumIO/feature/js_dev_setup

dev setup for bokehjs,