deep_merge throws an exception when it encounters integers about hashie

[jkeiser]

This appears to be because integers do not have metaclasses to attach methods to. The solution is probably to make deep_merge recurse when an object does not implement deep_merge, rather than attaching the method to the object.

[danielsdeleo]

I'll also point out that adding new methods to objects at runtime clears the method cache (on MRI; rbx and jruby have more fine-grained caches, but there's still some overhead) which causes a noticeable performance hit. If this library is intended to be used in a webservice or any other use case where performance is important, I'd advise against any implementation relying on include or extend.

[dblock]

Resolved via #132.