Fixed bug causing slug to mutate input. Still optimized.
Gemspec gardening.
Remove Ohm::Contrib::VERSION unused constant.
Update dependencies.
Update test helper.
Update slug tests.
Merge pull request #20 from frodsan/remove_version_constant

Remove Ohm::Contrib::VERSION unused constant.
Merge pull request #19 from frodsan/gemspec_gardening

Gemspec gardening.
Fix email in gemspec
Merge pull request #18 from luiscvega/master

Fixed bug causing slug to mutate input. Still optimized.
Fix code example on README.
Update Ohm::Timestamps tests.
Fix Ohm::Timestamps tests.
Update Ohm::Scope tests.
Update Ohm::Callbacks tests.
Fix Ohm::Callbacks tests.
Update Ohm::DataTypes tests.
Casts symbol only if exists.
Remove unneeded check. Ohm 2 doesn't save values for attributes set to
false.

Related commit
https://github.com/soveran/ohm/commit/717080fdb9ab9f71ee19cf84650dd6e5f6cc1789.
Use stabby lambda syntax.