Add ModuleMethods#original_instance_method

The public interface of adamantium infected classes now allows to
receive the original unbound method instance via
Class#original_instance_method(method_name)
Adjust flay score
Refactor memoized_method registratio to use default proc
Remove testing under 1.8
Use source location as equalization criteria for rbx

RBX equalizes UnboundMethod instances via identity
Use Hash#[] to trigger default proc
Merge pull request #16 from mbj/store-original-method

Store original method
Fix code formatting and comments
Upgrade gem dependencies
Update travis config to match other gems
Update flay threshold
Kill mutations in Adamantium.included

Add better specs and remove unneeded guard.
In all cases Adamantium::ModuleMethods is included, nobody should pass
in non Module!
Reset visiblity

Accidentally leaked this refactoring into prev commit.
Kill mutation in Adamantium#memoize
Kill most mutations in Adamantium::Flat.included