WIP: Support for Riak 2.0

This pull request attempts to resolve https://github.com/basho/riak-chef-cookbook/issues/94.

In addition to Riak 2.0 support, the following issues have been addressed:

- https://github.com/basho/riak-chef-cookbook/issues/51
- https://github.com/basho/riak-chef-cookbook/issues/105
- https://github.com/basho/riak-chef-cookbook/issues/106
- https://github.com/basho/riak-chef-cookbook/issues/120

## Tests

**Passed**:

- default-ubuntu-1404
- default-ubuntu-1204
- default-debian-720
- default-centos-65
- default-centos-510
- default-fedora-19
- source-ubuntu-1404
- source-ubuntu-1204
- source-debian-720
- source-centos-65
- source-centos-510
- source-fedora-19

**Failed**:

**Untested**:

- [ ] custom-package-ubuntu-1404
- [ ] custom-package-ubuntu-1204
- [ ] custom-package-debian-720
- [ ] custom-package-centos-65
- [ ] custom-package-centos-510
- [ ] custom-package-fedora-19
- [ ] custom-repository-ubuntu-1404
- [ ] custom-repository-ubuntu-1204
- [ ] custom-repository-debian-720
- [ ] custom-repository-centos-65
- [ ] custom-repository-centos-510
- [ ] custom-repository-fedora-19
- [ ] enterprise-ubuntu-1404
- [ ] enterprise-ubuntu-1204
- [ ] enterprise-debian-720
- [ ] enterprise-centos-65
- [ ] enterprise-centos-510
- [ ] enterprise-fedora-19