This includes changing to SASS from LESS, some HTML and some js files.
Key changes are:
Replaced the LESS with SASS, which is more complex but offers greater flexibility and features
Based on the sass-twitter-bootstrap project
SASS Changes to output all units (except for the sprites for the icons) as rem units, with px as a fallback. rem units have an 80% global support from browsers data from caniuse.com
References regarding the use and understanding of rem units.
Bootstrap was made to not only look and behave great in the latest desktop browsers (as well as IE7!), but in tablet and smartphone browsers via responsive CSS as well.