0.0.204

This version appears to have the parallel implementation at the frame level working perfectly. All tests passed. Now we need to start implementing the nice output functions, writing output files, and data analysis.

• Changed version file to 20.204
• added reference to default method
• some changes in the example files
• removed sides from FrameData
• fixed initialization of nsamples for self
• fixed definition of npairs inside
• implemented the self parallel and joined the common code with the serial version
• removed debug printing and fixed definition of sides in mddf_frame
• fixed random count sum
• returned linkedcells to serial, and almost done with the implementation of the parallel over frames using spawn