add .less

I've added less files for existing css. Less files use bootstrap variables and generate css files with very few differences from existing ones:
- spacing/comments
- typeahead: ```.twitter-typeahead .tt-hint``` slightly different color (I suppose you've modified it manually, there is no such color in variables.less)
- typeahead: ```.tt-suggestion.tt-is-under-cursor``` very different colors (maybe I've used wrong bootstrap variables?)