Simple packetization based on best practices.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Packet delimiter is 0x00.

Packets are encoded using COBS:

https://www.embeddedrelated.com/showarticle/113.php
http://en.wikipedia.org/wiki/Consistent_Overhead_Byte_Stuffing
http://conferences.sigcomm.org/sigcomm/1997/papers/p062.pdf

Message integrity is protected by the fletcher16 checksum:

uint16_t Fletcher16( uint8_t *data, int count )
{
   uint16_t sum1 = 0;
   uint16_t sum2 = 0;
   int index;

   for( index = 0; index < count; ++index )
   {
      sum1 = (sum1 + data[index]) % 255;
      sum2 = (sum2 + sum1) % 255;
   }

   return (sum2 << 8) | sum1;
}

Implementations may limit the packet size (to be able to use smaller buffers
and to have a simpler COBS implementation)

PC is master and arduino is slave. The protcol is synchonous, this means that
the master must wait for a reply from the slave, before it can send a new
command. If no reply is received (because either the request didn't come
through or the reply didn't come through) the original request must be sent
again. Slave MUST:

- preform the command, if it didn't get it earlier and send a response

- resend the response if it already processed the command earlier.

Current and next request can be distinguished by EVEN/ODD marker at
start of all packets except RESET.

After a RESET, the slave MUST send a RESET back and expect
the first command to be even (and reply RESET to ODD commands until it has processed
an EVEN command).

EVEN = AA
ODD = 55

EVEN/ODD is denoted by 'EO'

All packets start with an even/odd marker, except RESET.

RESET from m -> s and s -> m
~~~~~

Packet (zero length)

0000:

Note: a RESET only resets the communication state, not the whole arduino

PING from m -> s and PONG from s -> m
~~~~

Packet (length = 1)

0000: EO


other packets (free form, length > 1) m -> s, s -> m
~~~~~~~~~~~~~

0000: EO xx yy zz


Version 1 commands
~~~~~~~~~~~~~~~~~~

00:          	read blower value

01 XX:       	set blower to XX

02 XX YY ZZ: 	set RGB color leds to XX YY ZZ

03:          	read last IR command

04 XX:	     	write releas pin

05 XX:		write visjeslicht pin

06:		read releas pin

07:		read visjes pin

08:		read RGB color leds