Build select2-bootstrap-css on Twitter Bootstrap v3.2.0.

Update development dependencies:

 * Twitter Bootstrap from v3.0.0 to v3.2.0
 * respond.js from v1.2.0 to v1.4.2
 * jlong/sass-twitter-bootstrap to twbs/bootstrap-sass

Adjust paths in Makefile, fix glitch when copying Bootstrap fonts to _jekyll.
Adjust paths in lib/build.scss, build.less.
Update Less patch.

Update readme - one known issue has been fixed in Bootstrap itself.