Capistrano deploys require the Gemfile.lock file to be in source control

The command: ```bundle exec cap staging deploy``` was failing with the following.  This is happening because Canvas sets up a trick in Gemfile so that we can alter the actual gems used at runtime by populating the Gemfile.d directory.  However, Capistrano knows nothing about that and tries to release using what is in source control by running ```git archive bz-staging | tar -x -C /var/canvas/releases/<someReleaseDate>```.

```
DEBUG[ecd43370] Command: cd /var/canvas/releases/20141113171953 && /usr/bin/env bundle install --binstubs /var/canvas/shared/bin --path /var/canvas/shared/bundle --without development test --deployment --quiet
DEBUG[ecd43370] 	The --deployment flag requires a Gemfile.lock. Please make sure you have checked
DEBUG[ecd43370] 	your Gemfile.lock into version control before deploying.
cap aborted!
```