v1.5.0, 6/27/10 -- Initial Packaging. Fully restructured into a unified API with tests.
v1.7.0  6/29/10 -- Now supports both Series 1 and Series 2 modules 
                   (the API turned out to be the same). Additionally:
                   * API frame logic was split into its own class, APIFrame
                   * XBee renamed to XBeeBase
                   * XBee1 renamed to XBee
                   * Tests updated to reflect changes; API frame tests
                     moved to test_frame.py, now test APIFrame instead of
                     XBee base class
                   * Test files renamed appropriately
                   * PyLint score improved
                   * Various docstring updates
                   * Updated example code to reflect changes
v1.7.1 7/7/2010 -- Bug fix: Now supports receiving I/O data with 64-bit addressing
                   * Previously, an exception was raised when a packet with ID 0x82
                   * arrived, which contains I/O samples with a 64-bit source address
                   * This has been fixed.
v1.8.0  7/8/10  -- Implemented threading support
                   * If a callback method is given to the XBeeBase constructor,
                     a new thread will automatically be spawned. This thread
                     will read from the serial port and call the given callback
                     method whenever a valid data packet arrives.
                   * XBeeBase.halt() was added. This method ensures the proper
                     shutdown of a separate thread if one has been spawned.
                     This method must be called before closing the serial
                     port used by an XBee instance in order to prevent
                     improper use of the serial port.
