Import calibration load script

This script uses the serial number of the attached kinect to identify the turtlebot that is currently connected and attempts to load a calibration file for it from a standard location.
Needs more work to detect an xtion plugged in instead of a kinect, as well as if neither are plugged in.
Attempt to use the usb to serial converter's id

If the robot receives a velocity command we'll assume that it's been
brought up and must now move.  If we don't have the kinect's serial number
yet assume we won't ever get it.  Instead attempt to find a calibration file
that matches the serial number of the usb to serial converter that should be
attached at /dev/ttyUSB0.  This setup will prevent the calibration script from
running indefinitely waiting for a kinect that might never come.
Bug fixes
Merge pull request #14 from kbogert/calibration

Automatically load calibration parameters from a .yaml file
Remove open() to fix double-open exception. Improve error info when an exception on opening serial port happens
Merge pull request #18 from PaulBouchier/indigo

Fix issue #17: open() throws exception.