Implement error handling utility

The [`try`](https://github.com/Aweary/microbe.js/blob/master/microbe/response.js#L6) method is mentioned but doesn't actually exist yet. Needs to be implemented. Error handling should:
1. Route all errors to a central location for consistent handling
2. Be user configurable and catchable

Start in microbe/response.js at the referenced try method and read the surrounding response and error-handling flow. Trace how errors currently move through the Node.js framework, then compare the design against the requirements for central routing, user configuration, and catchability. Done means the try utility exists and all three behaviors are covered.

Written by the indexing model from the issue text.