Merge api_errno into api.py.

api_errno should not be its own separate module.
Improve documentation and style of path stripping middleware.
Document API errors
Document API methods

The old curl docstrings are now examples.
Consolidate individual calls to return errors into _jsonStatus()
Make all calls to bottle explicit
Replace code duplication with _ok function when things go to plan
Return 201 for created slides, or 422 if the times are wrong.
Use argparse to handle passing args to API
Add argparse to requirements
Start writing nose tests -- firstly testing API statuses.
Test trailing slash is irrelevant to data returned
Test name path -> slash
Test 404
Test bad method
Test for bad args when no post data
Add malformed/missing args tests
Flush database before each test
Test empty multi slide retrieval
Test adding a slide and then doing a multi retrieve