Add sentry-fogbugz to the list of 3rd party plugins

FogBugz is a bug tracking system built by fogcreek. This plugin allows you to easily create Fogbugz cases from events within Sentry.
Merge pull request #1272 from glasslion/master

Add sentry-fogbugz to the list of 3rd party plugins
Merge branch 'master' into bootstrap3
Correct release activity
Correct is_managed reference