Add support for import event API.
Make the message format extensible to handle data and api_key cleanly.
Remove an extra comma.
Add support for optional params for People class methods.
Add missing property alias to create_alias calls.
Fix failing tests due to timezone incompatibility.
events.import now accepts api_key and its not required by Tracker initializer.
Add test coverage for import, and fix failing tests due to changes in message structure.
Reflect import method signature change in comments.
Merge branch 'master' of github.com:rubymerchant/mixpanel-ruby into 1.0.0rc
Changes for merge to master from Pull Request #9

AWESOME PULL REQUEST! Thanks, @rubymerchant!

Changes include:
- Serializable, string format for new messages

This makes passing messages between processes and
onto work queues very easy, which is a goal of the
library.

- Unbuffered imports for BufferedConsumer

Mostly to keep BufferedConsumer code simple- as things
stand, the expected use case for imports is in batch,
which can live without buffering.
Start changelog in Readme.rdoc
Clearer tests and correct docs for union
Version bump