trimmed unused gems and upgraded dev/test gems
Fail when both arguments to pgbackups:transfer resolve to same DB
Merge pull request #1182 from deafbybeheading/avoid-dangerous-self-transfers

Fail when both arguments to pgbackups:transfer resolve to same DB
Merge pull request #1180 from heroku/rm-gems

trimmed unused gems and upgraded dev/test gems
Convert specs to RSpec 3.0.4 syntax with Transpec

This conversion is done by Transpec 2.3.6 with the following command:
    transpec

* 19 conversions
    from: == expected
      to: eq(expected)

* 19 conversions
    from: obj.should
      to: expect(obj).to

* 2 conversions
    from: obj.stub(:message)
      to: allow(obj).to receive(:message)

* 1 conversion
    from: obj.stub(:message => value)
      to: allow(obj).to receive_messages(:message => value)

For more details: https://github.com/yujinakayama/transpec#supported-conversions
prevent uploading to beta releases older than the current release