Add change log for changes since git

[Ericson2314]

Fixes #9

[Ericson2314]

Additionally I tagged each release in the fork. Just do:

1. git remote add obsidian git@github.com:obsidiansystems/groups
2. git fetch --tags obsidian
3. git push origin v0.4.1.0 v0.5.{1,2,3}

To add them to this repo.

[Taneb]

Thanks very much for this :D I'll admit I've been procrastinating this a little (half a year) too much