renamed save/load partitionmap c++ functions
added comments
renamed checkpoint to partitionmap; added a test
whitespace cleanup
no longer assign partition IDs to single reads
cleaned up _validate_partitionmap calls
rearrange hashtable.cc functions a bit
fixed my braindead load_partitionmap function
more graph tests with a string of random, connected sequences
removed test output\!
added test data output
added cryptic comment
added script to extract partitions into group files
subset stuff half-working
fail to understand partition_map/master_map stuff.  o well, for later.
expanded Python API a bit
basic subset approach is done and confirmed on 25k; breaking on 100k
failed attempt to get subset partition merging working
subset partitioning working better, although not completely
fixed more problems with subset partitioning, added tests