Escape charm code for safety and usability.
Fix bundle test.
Merge pull request #18 from garyposter/fixCodeDisplay

Fix nasty XSS and usability bug in charm code display.

To QA, look at http://localhost:8888/precise/mediawiki-10/#bws-code and choose the hooks/db-relation-changed file.  You should now see the whole file.  Compare this with the output on comingsoon or jujucharms.