failure to restart image stream

[touretzkyds]

Due to WiFi unreliability, it's not uncommon to momentarily lose the image stream. Once this happens, we never get it back. This is due to a bug in WSImageThread's run() method.

After doing

    self.ws.connect(self.uri)

we need to do

    self.start_stream()

[touretzkyds]

I've submitted a pull request with the proposed fix.