0.9.6

- stopped automatically loading last file on program start.
- open file defaults to image formats instead of ngc files.
- image_dpi now remembered between sessions
- image_dpi slider has more realistic upper limit
- some float values were being rounded to produce really long strings
that messed up the arduino.  they've been fixed to two decimal places.
- feed_rate is now passed to jogging controls more accurately
- gcode is now dumped into temp.ngc every time.  save the file
somewhere else if you want to keep the gcode.