Changed in/out of extensions to a map.

Was formerly a vector, but that gets super fiddly fast; a map you can
easily add a new keyword if you need to.

Renamed the keyword for the function to modify the tree :process-code
instead of :modify-tree.
Changed extensions to use map in/out.

Edited apply-all-extensions as well. apply-all-extensions returns the
modified map, but also has a :text keyword, with the original text.

Also, a couple of the extension tests fail. That's not idea but I'm more
concerned with setting up a structure at the moment, rather than the
actual tree transformations.
Typo in landing template.

Error in html; missing >. Fixed.
Removed comment-breaker from folder.

Was just cluttering it up.
Changed extensions to be statically referenced.

I was trying to set this up to try deploying it to heroku, but
unfortunately there's all kinds of Messiness that's involved in
dynamically scanning the jar for the extensions. In the end I decided that
if I'm just going to pack these things into a jar anyways, what's the
point of writing it so you can just drop in a new extension?

See, the original idea to reading the folder was that it would make it
easy to extend, but then instead of using it like an application I ended
up packing it into a jar.

So, if you need to add a new extension, you'll have to go into
extensions.clj and manually add it to the list of all extensions. I
suppose I could add in a step to auto-generate the code...but the project
isn't nearly complex enough to warrant that, yet.

This will obviously break the tests.
Updated tests to work with new extensions.

I have a serious case of name cluttering; there are way too many things
that are named "%extension%" at the moment.