Optimize methylation extraction with MethyDackel

[Nick-Eagles]

The MethylationExtraction process in the second module, which uses MethylDackel, contains serially executed code that could benefit substantially from (embarrassing) parallelism. In fact, some testing demonstrated that the methylation extraction itself takes less than half the total time for the process on a typical sample. Splitting the cytosine report by chromosome should likely be done in a separate process, so that it can be parallelized across chromosomes and run concurrently with the summary stat calculation, which typically takes roughly 30 minutes per sample.