This PR was merged into the 2.0.x-dev branch.

Discussion
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Added support for callables in CallbackResolver

Added the ability for the callback resolver to support any callable instead
of just the object and method callable type.

An alternate implementation to this would be to update the CallbackResolver to use an interface, then keep the old CallbackResolver as is and just add a new implementation that you can change if you'd like. I'd probably prefer to do the interface, but depends on what people think.

This fixes #1327
Signed-off-by: RJ Garcia <rj@bighead.net>

Commits
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65afac9f Added support for callables in CallbackResolver