Release 1.2.0

Features:
- Add geppetto `.project` natures
- Add GH auto-release
- Add `apt::key::key_options` parameter
- Add complex pin support using distribution properties for `apt::pin` via new properties:
  - `apt::pin::codename`
  - `apt::pin::release_version`
  - `apt::pin::component`
  - `apt::pin::originator`
  - `apt::pin::label`
- Add source architecture support to `apt::source::architecture`

Bugfixes:
- Use apt-get instead of aptitude in apt::force
- Update default backports location
- Add dependency for required packages before apt-get update
Merge pull request #141 from hunner/release_1.2.0

Release 1.2.0