QTR RC all 4 sensor test

Some test code that calibrates and then displays data of all four IR
sensors. Two are actually the analog kind, but the internal comparator
on the Arduino digital pins makes it look like a digital sensor.
Changed calibration LED and small changes
Interrupt example code added

Basic interrupt code triggered by an analog IR sensor connected to pin 2
(which is the Arduino's external interrupt 0).
Adding QTRSensors library
created 'libraries' directory to separate arduino library code from our code
Cleaned up main sketch file.
removing unsused variables
Skeleton code for odometry
Added PinChangeInt interrupt library and test code.
In progress odometry code
Both wheels interrupt example

Just a quick example utilizing the the new library Ryan found to make
any pins into interrupts and use them to asynchronously track the number
of encoder wheel edges and therefore each wheel's traveled distance.
Removed most of the Ping sensor code to simplifiy things.
Fixed the pin numbers for the sensors
work in progress
small changes
Turning code
bug fix
Haohan's odometry; fixed type casting error

define DIAMETER will look like an int to the code and so it casted the
result to an int instead of float
more changes and position equations
Merge branch 'odometry' of https://github.com/rmmccann/CS503-Robot-Controller into odometry