Adds optional opts to start command, which allows passing Binds and LxcConf as per http://docs.docker.io/en/latest/api/docker_remote_api_v1.5/#start-a-container
Fixes the Content-Type field for json requests
Merge pull request #4 from EricMCornelius/master

Adds opts to the start command and sets the Content-Type field appropriately for json POST requests