Add --rebase_motifs option for speeding up filtermotifs step

[jbeaulaurier]

• mbin version: 1.0
• Python version: 2.7

Feature request

It would be very nice to have an alternative means to completely de novo motif detection. Instead of querying a massive space of all possible k-mers and bipartite motif configurations (several hundred thousand), it would be nice to be able to only gather IPD scores for the ~1000 motifs that have been previously identified in bacterial methylomes and are present in the REBASE database. Applying this option would greatly speed up the filtermotifs pipeline.