Merge pull request #83 from bgamari/fixes

Some of these are small changes extracted from @triffid's std::string -> char* conversion which are worth on their own. Each patch is small, self-contained, and hopefully pretty non-controversial.
version change
Robot: remove unused variable
USB DFU: keep usb connected while we respond to reset request.

we also become a kernel module so we can receive the on idle event. This would be an ideal place to do shutdown tasks, eg save position somewhere
Extruder: make sure we have a block to release, avoid segfaults
utils: is_alpha, is_digit, is_numeric, is_alphanum, is_whitespace utility functions
Gcode: get_int method to shortcut string->float->int conversion
SlowTicker: implement G4 pause
TemperatureControl: PID resets I to 0 if output exceeds bounds to reduce anti-windup effect
Secret Sauce for windows to activate the driver it comes installed with
added make dfu
TemperatureControl: Use median smoothing instead of mean