Merge pull request #1 from postaljs/master

Update from upstream
Ensuring context set for delayed callbacks
- also, fixing standalone test runner
Added context tests for limited callbacks
- properly running the delayed context tests
- formatting
Ensuring context in self-disposing callbacks
- allowing context modification after delayed configurations
Merge branch 'subscription_fixes' of https://github.com/dertseha/postal.js into dertseha-subscription_fixes
Updated mocha assets, fixed problem with uncleared setTimeout (causing mocha to report a failure when there was not one), changed var that = this to use 'self' instead of 'that' (for consistency).
Added @dertseha to contributors list in package.json. Merges #44 (and closes #44).