Create the input files for Art Palmer's CPMGFit program.
dir: The directory to place the files. If not given, this defaults to the model name in lower case.
force: A flag which if set to True will cause the files to be overwritten if they already exist.
binary: The name of the executable CPMGFit program file.
spin_id: The spin identification string.
The following files are created:
One CPMGFit input file is created per spin and named `dir/spin_x.in', where x is the spin ID string. The file `dir/run.sh' is a batch file for executing CPMGFit for all of the spin input files. If you would like to use a different CPMGFit executable file, change the binary name to the appropriate file name. If the file is not located within the environment's path, be sure to include the full path in front of the binary name so it can be found.