Addition of interrupt code

Interrupt code addition. Needs to be tweaked and tested. Upon initial
setup the slave will sleep. After this it will then wait for the
interrupt on pin 7 as LOW. It will then wait for serial data. Once
printed it will then go back to sleep.
Clean up code and add interrupt pin

Normal clean up and interrupt pin set to pin 7. Now need to test and
then rip out the main JSON/trim operations in to its own routine to keep
Loop() clear
Pin change

Pin was incorrect
Interrupt Addition

Added in our interrupt code. Tested using arduino uno as slave. Need to
add in fail safe of loops before sleeping on its own again if no data
received as it should be
Changes to file format

Nothing else to add
Loop counter

Addition of a loop counter to knock the slave arduino back out if there
is no data received from the master
Merge pull request #4 from christoface/Slave-Interrupt-Integeration

Slave interrupt integeration