Wiki: Updated docs

Updated the Sizzle docs to better fit the jQuery documentation style guide. Also fixed a number of syntactical and spelling errors.

Unfortunately, GitHub is a little weird in regards to Wiki contribution for non-org-members, so I've had to disguise these changes as a modification to the documentation link path in README.md (didn't bother branching it). Have filed a bug report with GitHub. 

The actual changes are in https://github.com/neftaly/sizzle/wiki (https://github.com/neftaly/sizzle.wiki.git). Suggest doing a manual pull/push on sizzle.wiki to keep the changelog intact, though you could also just copy & paste [Home.md](https://github.com/neftaly/sizzle/wiki/Home.md).

Thanks!