Add @schedule decorator for CloudWatch-triggered events #234
First pass at solving Issue #231. It adds a new decorator that lets the user specify functions as the handler for CloudWatch timed alerts. Chalice can send handle periodic events at intervals of 1 minute or greater with crontab fidelity.
If this pull request can be accepted (with whatever code review changes requested) I will write documentation and more tests.
CloudWatch allows quite a few more rules based on pattern matching of events, but I was focused on (what I assume) is the most valuable use for Chalice: timed events.