Use Bootstrap tooltips to give info on buttons/etc in the viewer application

[fedarko]

This'll help make it clearer to the user what these controls do, reducing the need somewhat for inline documentation (although that could still be helpful).

[fedarko]

Not really sure how much of this is necessary, though -- the only confusing parts of the application I can think of are the rotation selector and the fit selected button, and the rotation selector can be easily explained inline in the progress bar (and the fit selected button can be explained in some README/tutorial, #30). For now I think it's a good idea to focus on other things -- we can add tooltips easily if we'd like to in the future.

[fedarko]

This issue was moved to marbl/MetagenomeScope#29