Fixed gate by Updating Gemfile to pin Rake to 10.1.1

The latest Rake update requires Ruby >= 1.9. Bundler in the
current gate uses 1.8.x. This update fixes the gate by pinning
Rake to the last known working version.

Change-Id: Iac17385f45319e98253a7513182370005240621c
Merge git://github.com/puppetlabs/puppetlabs-keystone