Update CHANGELOG and version for 0.9.5
Update Gemfile for testing against Vagrant 1.7.1

Also required bumping `vagrant-spec` to `1df5a3a`. Vagrant 1.7.x expects the
dummy provider used in spec tests to respond to additional methods such as
`state`.
Add support for PE 3.7.0

Also bump `LATEST_RELEASE` to point to 3.7.0.

PE 3.7.0 adds support for two new platforms:

  - SLES 10
  - Windows 8
Set up for testing with Travis CI