Issue #13: Validate redirects

* Add redirects to the common schema

* Initial support for the `items` schema key for validating arrays

* Tests
Merge pull request #20 from lmorchard/13-redirects

Issue #13: Validate redirects
Remove `redirects` from todo list, add a testwatch script for npm that runs tests on file change
Add note to README.md about testwatch
Close #17: Validate required_features
validate origin
added describe per property