Revision 2

Changes:

- 10 mil traces, no 90° bends, ground plane where possible.
- Font size for pin labelling increased.
- Removed SWD port to reduce complexity and size. If needed, the board
can be accessed at the broken out pins.
- Included 3.3V regulator, since the driving ability of those includede
in the USB to serial converters is limited.
- Removed debouncing cap from reset switch.