Use bootstrap from git submodule instead of ours.

Since 98c270853d0b299cc0abccecd5ee73f43d4705c4 we were using a version
carried away from long ago. Bootstap and jQueryUI have some clashes that
were fixed from 2.2.1 onwards. Now we use the correct version.
Merge pull request #196 from inaes-tic/bootstrap-version

Use bootstrap from git submodule instead of ours.