Remove 'photonstorm.zip'

This is removed for the same reason you remove compiled binaries from
Git.

In the future, this zip will instead be compiled automatically for each
release.
Remove 'Flixel Versions' and replace with SWC of current Flixel version
Move 'Test Suite' to separate branch, while moving actual code to 'src'
Move 'Docs' to separate branch
Fix repository structure

Now it's more like other Git repositories, but more importantly, easier to manage.
Add required 'neoart' libraries

As SWCs, of course.
Add gitignore

Taken from https://github.com/FlixelCommunity/flixel/blob/dev/.gitignore

Ignores AS3-specific ignores, as well as some general "OS-specific"
files.
Import changelog from 'test-suite'

It fits in better here instead
Convert CHANGELOG to Markdown

Yay! More fancy!
Update "Quick Install Guide"

It's now even quicker to install! :D
Convert License to Markdown

Well, a tad prettier.

Also, fix cut off part of license in README.
Merge pull request #18 from FlixelCommunity/master

Fix repository structure