- introduced automatic reconnection after 65s of no data and no ticks re...

...ceived from Meteor

- introduced a new method call on stream consuner: on_header where the http headers are received at connection time. This allow us to check the header.
- introduced an optional argument to the constructor of class User "stream_base_url" which is set to the standard url: stream.datasift.com
- fixed a problem where on an http error the raw socket cannot be obtained as it was not created and the error message is crytic. A more understandable message is now displayed. This might need to be revisited.