Sets a default statusCode of 200 for all API Gateway requests

[mattbeattie]

Problem

For all API Gateway requests, a statusCode is currently only sent if it's an error. This is because the only thing developers have access to when handling a route is the response body (which is stringified and placed on the response here).

Proposed Solution

Given that any error sets the statusCode accordingly, it should be safe to assume a default statusCode of 200.

This PR does the following

• Sets a default value for the statusCode of 200 when handling API Gateway requests
• Updates the corresponding unit tests to ensure that the response also includes the statusCode

[coveralls]

Coverage increased (+0.04%) to 95.763% when pulling 37a9f96 on mattbeattie:sets-default-statuscode into cc7367d on doomhz:master.

[coveralls]

Coverage increased (+0.04%) to 95.763% when pulling b01fa89 on mattbeattie:sets-default-statuscode into cc7367d on doomhz:master.