Client code hangs if server unavailable

Client code currently waits forever for a response from the Lasair API.  (Somewhere around line 37.)  This causes the calling code to hang indefinitely.

It would be great if:

* There was a timeout with a default value (e.g. a few seconds?)
* The timeout could be overridden by the user (e.g. when creating an instance of lasair_client.)
