assets: require.js + uglify.js

* Updating webassets and Flask-Assets to 0.10-dev.
  BROKEN see: https://github.com/miracle2k/flask-assets/pull/67

* Hacking the assets extension to remove the initial "/" to js modules
  otherwise r.js is confused.

* Grouping the invenio.js with bootstrap.js.
  It's a PROOF OF CONCEPT! THINGS ARE GONNA BREAK!!

* Using require.js in dev and almond.js in production.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>