Add escape hatch for supertest to mock http.

Supertest tests express views using the builtin http module, the one we
mock away. To not break this, make the http mock detect supertest, and
let it pass through.
Reset mock config after every test, misc fixes.

This fixes the final failing test.
Merge pull request #42 from mythmon/test-0.8-failures

Fixes for running tests on node v0.8.14 (Travis)