Require serializers and paginators

[KorvinSzanto]

I like the idea of splitting these repositories out, I think we should wait until v2.0 to exclude them to lower the barrier to 1.0.

[matthewtrask]

I like this, especially with it being more of a 2.0 goal. But we should figure out whats up with the test suite.

[Nyholm]

Im not sure it is a good idea to make these all required.

[KorvinSzanto]

@Nyholm Can you be specific about your concerns? The idea is to require these until v2 to ease the transition to the separated repositories.