Update rvmrc and gemset
Use less-specific version for dev deps.

Also:
- Updated copyright date.
- Updated hoe and minimum Ruby versions.
Bump minor version, update history.
Added signature for changeset 96a833abcc47
Added tag v0.2.0 for changeset aa7753756e7b
Fix the license setting in the gemspec.
Bump the patch version, update history.
Added signature for changeset 0621f704d94a
Added tag v0.2.1 for changeset 4c6a1a558af0