Removed stale CodeMirror mirror.
Made it work with CodeMirror 3.0
Rewrote docs to reflect rewrite (v 0.3.0)
Removed extraneous print.
Improved docs.
Added all other options for CodeMirror except keymaps.
Removed unused import.
Merge pull request #6 from cag/master

Rewrote it to have it work with CodeMirror v3.0