Don't wait forever for serial output when reading FW version

[mrcity]

I don't think a timeout was implemented in the code, so if the Python program doesn't receive any data back from a firmware version poll, it'll hang until it finds 3 bytes of data. The preferable fix would be to read all input within 1 second of the request (whether 3 bytes or not), then stop.

[mrcity]

A timeout has been hard-coded so that the serial read will expire after two seconds. This variable should be placed into a global instead of hard-coded in several different places. However, the original issue (of application hanging) is resolved as of 1.2.1a.