closes#422, issue #295
- Added GFM mode to codemirror
- Took the github.js extension for Showdown and added all useful behaviour
- Now supports strikethrough, line breaking and
multiple underscores, and auto linking urls & emails without breaking
definition urls
- Also added definition url handling in preparation for #295
- Added unit tests for the extentions individually and integrated with
showdown
baac3a34c2