Add timeout capabilities

[claudioseveri]

In time-sensitive applications (e.g. a sensor that uploads data every minute) a timeout feature in data reads and writes to the server might help dealing with slow internet connections, ensuring that the function never exeeds a certain time duration.
Python module "requests" already supports this, so it's only a single-line edit to do.

[bachwehbi]

Good point!

I would like to keep the API coherent with the rest of Beebotte SDKs.
Thinking about adding the timeout as a parameter of the BBT object, something like:

bbt = BBT( _accesskey, _secretkey, hostname = _hostname)

timeout = 6 # 6 seconds
bbt.setTimeout(timeout)