paginated_context

I'm a bit surprised that this turned out to be so complicated, and I'm
not really happy about this business of raising and catching a custom
exception, but I don't quite see how to do better??

[#21]
revised directory structure for views

I wasn't happy with how our views.py was getting so bloated. This
commit breaks it up into multiple files within a views/ directory:
helper functions and classes will live in views/view_utils.py and
views that don't return HTML will live in views/service.py. Flake8 was
helpful for cleaning up the imports.
@paginated_view decorator, and Previous/Next links in template fragment

Instead of having to do that ugly "try/except PaginationRedirection"
inside of every view that will have pages, let's write a decorator for
it!

[closes #21]
Merge pull request #25 from zackmdavis/generalized_pagination_and_view_utils

reuseable pagination, and reorganizing views