Fix for embedding code from github
Add option for custom js (like custom css)

* Add a new 'js' flag to indicate you want to embed a file named 'custom.js'
  which should exist at the root of the wiki
[[_]] float clearing tag experiment
Merge pull request #662 from lemonsqueeze/clearfloats

[[_]] float clearing tag experiment
Fix style
Merge pull request #661 from simonista/custom-js

Add option for custom js (like custom css)
Update README.md
Update README.md
Merge pull request #660 from simonista/fix-github-links

Fix for embedding code from github