Upgrade jQuery to 2.1.3 and remove CDN dependencies

  - Upgrade jQuery to 2.1.3 (no more IE8 support, but lighter)
  - Inlined treeviewer CSS (1 less HTTP roundtrip)
  - Moved libs to `frontend/vendor` to rid of copying jquery-ui around
  - Fix #191

**Warning:** some styles have changed and colors look slightly different now. Feel free to test and give feedback.