Remove all the signal handlers, it'll be clearer inline. Write a query_is_unique function to work out where we can actually do a unique lookup

Conflicts:
	djangae/db/backends/appengine/commands.py
	djangae/tests.py
WIP - Start implementing the context cache

Conflicts:
	djangae/tests.py
Fix a failing test and revert some cleanup that wasn't

Conflicts:
	djangae/db/backends/appengine/commands.py
	djangae/tests.py
Fix a broken test

Conflicts:
	djangae/tests.py
Implement the context cache, fail to write tests
Add a replacement for mock, because mock makes me sad

Conflicts:
	djangae/tests.py
Clean up sleuth, replace mock-calls so that the tests actually work
Docstrings
Switch mock for djangae.contrib.sleuth. Linting things.
Fix a bunch of issues with the context cache and querying in general

Conflicts:
	djangae/db/backends/appengine/commands.py
Make qs.none() do the right thing

Conflicts:
	djangae/db/backends/appengine/commands.py
When building a multiquery, reconstruct the queries but disregard any keys_only flags
Make sure starting/ending a transaction wipes out the context cache
Add a couple more tests to the inheritance stuff
Adding a test to make sure that the context cache is cleared between requests.  Removing unnecessary/unreferenced `global` declaration.  #55
Code tweaks
Merge pull request #55 from lukebpotato/caching-impl-rebase

Implement context caching