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

Discussion
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Allowing callables for mount

- Added the ability to pass callables into the controller collection
    mount method.
- Updated documentation to show usage of new callables in mount and
    recursive mounting.
- Added appropriate tests

This addresses #1262 and #1290
Signed-off-by: RJ Garcia <rj@bighead.net>

Commits
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847b7eeb Allowing callables for mount