Modified Param.compareTo to handle null properly

Large modifications to Driver
    - write is now private
    - Added public method sortAndWrite
    - Added logic to sort input lists based on their sizes
    - Fixed meld logic
    - Added private helper method findMin for n-way merge

Updated MeldTest class
    - Refactored test to simpleMeldTest
    - Added new test complexMeldTest
    - Added input files for complexMeldTest

Updated ParamTest class
    - Replaced references to Driver.write with Driver.sortAndWrite

Added input files for complexMeldTest