Use ZEIT Now's Serverless Functions

[k4m4]

Migrate from zeit/micro to ZEIT Now's Serverless Functions. For reference:

• Read the disclaimer at the top of zeit/micro's readme.
• now-dev should be used to run the development server.
• Currently, ZEIT does not provide an official way to write tests for the Serverless Function helpers. Here's an unofficial implementation: zeit-now-node-server.