Adds a `definition_extension` method to EnumeratedValue class

TODO Need some tests
Update degu.gemspec

tests are green for activerecord 4.0.0
Merge pull request #1 from TBAA/patch-1

Update degu.gemspec to allow rails > 4
Configures activerecord version

Also removes some deprecation warnings
Renames readme file to use markdown
Uses markdown file as readme
Configure travis to ignore fails on ruby-head due to a ruby-head bug
Adds tests for definition_extension method
Update README.md

Starting documentation modification
Update README.md

Continues documenting
Update README.md

Continues with documentation
Update README.md

Renamed Planet names
Update README.md

Adds documentation for has_enum
Update README.md

Adds documentation for has_set gem
Adds default params to to_json method
Merge branch 'master' of https://github.com/arfl/degu into arfl-master

Conflicts:
	Rakefile
	degu.gemspec