Use ArrayBuffer as base for MessageBuffer
Use TCP Protocol v2. See caveats.

Caveats:

- No AckEvents generated yet.
- Channels are subscribed to one-by-one.
- ReplayOnly not supported. This will not change.
Subscribe to Channel Groups where possible
Send AckEvents ACKs
Remove unused type
Merge pull request #6 from thenewtricks/tcp-protocol-v2

TCP Protocol v2

Some tweaks to Courage.js to support TCP Protocol v2.

- Strings map to Blobs under the hood
- MessageBuffer now works with an ArrayBuffer as its base instead of Uint8Array
  - Enabled better semantics when writing the Uint16 for a Blob
  - Also refactored the write* methods.
- Replay is now a client global: subscribeOptions

ReplayOnly is not supported, and won't be until there's a use case.