Return new message's ID from a push

Gracefully handle error responses with no body

Also close a few streams that were sloppily left open.

Use getErrorStream on HTTP errors

Bump version to 0.0.5

Add LICENSE

Fix get on empty queue

Closes iron-io#4

Merge pull request iron-io#3 from iron-io/batch-msg

Use new, batch message style API

Added link to downloads.