Update version numbers to 5.0.6
Update version history for 5.0.6
Remove documentation note from 5.0.6 list
Merge pull request #1405 from melissalinkert/5.0.6-history

Update version history for 5.0.6
Merge pull request #1393 from melissalinkert/5.0.6-version

Update version numbers to 5.0.6