Amends 81e78e8

Changes :
- Added link to gist for `mj()` to reflect deprecation of Jacket branch.
- Replaced use of "mixin" for "component" to reflect this fork's features.
- Fixed some sentences here and there.
Fixed mq-stringify

It wasn't working under certain circumstances in libsass, so the function was updated to a variant of the latest incarnation from SassyLists.