Updated MEME arguments, leiden init, dependency list

• Incorporates changes from PR #60, which added the -revcomp flag to MEME if "revcomp=True" was specified in TfModiscoWorkflow (is true by default), and also switched -mod to zoops (zoops stands for "zero or one occurrences per sequence"; this concords with the default for the web and also seems more appropriate for seqlets than the anr mode, which stands for "any number of repetitions")
• Updated the Leiden clustering to take the best of both worlds over the singleton initialization (i.e. what is done without preclustering using MEME) and the MEME initialization.
• Updated dependency list in setup.py to be more complete
• Updated the test suite. Attempted to add a travis build but it looks like installing MEME via travis is nontrivial.