Minor markup changes to syntax doc.

<pre><code> seems to be the standard way to do code blocks, and I
removed some dead CSS and formatted the rest to be easier to read.
Readme updates.

* Replaced FontAwesome icons with Polymer icons (requires an internet
connection to see them).
* Updated list of third-party software used in LOOT.
* Updated cleaning appendix to replace UDR with Deleted Reference, as in
LOOT's code.
* Removed unused Javascript.