Add dependency on bootstrap.css file

[fcagalj]

Update bower.json to add dependency on https://github.com/fyockm/bootstrap-css-only which holds bootstrap.css, to avoid installing regular bootstrap which depend on jQuery, or adding bootstrap.css manually.

[pkozlowski-opensource]

I don't think we should do this as it points to a non-official source and we don't have any guarantee that this source is reliable and up-to-date. For example, the last commit in the mentioned repo was done on Mar 20, the latest version is v3.3.4 versus released bs 3.3.5 etc.

[fcagalj]

Ok I agree, but issue should be solved or documented...