Export pageable interface to ease up mocking

[ebreiner]

The pageable interface was not exported but exposed in the client when retrieving the next page of pageable. This made mocking pretty tough.

[ebreiner]

Closes #171

[strideynet]

Does this actually make matters any better ? IIRC an interface with a unexported method cannot be implemented by another package. We'd also need to make canPage exported.

[ebreiner]

Your absolutly right.