switch to sockets.tcp for the socket provider

Tested with 'grunt integration', which verifies that basic tcp functionality works.
Note that manifests of chrome apps using this version will need to change per https://developer.chrome.com/apps/app_network
Style nit: Rather than binding to a string and then doing string lookups, I'd bind to the API itself. i.e. `this.socketApi = chrome.socket.tcp` and then use the socketApi call. Type inference is slightly easier that way.