Use my_rank for my_process.rank; add rank argument to print_elapsed_time
Do not import time;use new function build_alpha_dict;consistently use types for arguments word_len, start, stop;use types in build_dna_sparse_frequency_matrix
Remove pgamma_m_v and pgamma_mv_matrix from saftstats;rename pgamma_m_v_vector to pgamma_m_v
Make MPIsaftmain a Cython module;add types to selected variables
Change some variable names; tidy up formatting
Use saftsats.pgamma_m_v
Move common parts of saftmain.pyx and MPIsaftmain.pyx into new file saftstage.pyx