API: added method for randomly getting up to N seqs per sample
REL: scikit-bio dep
DOC: @adamrp's comments, and expanded notes/returns
MAINT: removed extraneous sorted
MAINT: using sys.maxint, thanks @adamrp
MAINT: rsplit instead of split, thanks @adamrpwq
ENH: min_seqs, preserve sequence id
ENH: the FUTURE!
DOC: update
Merge pull request #255 from wasade/random_subset_seqs

API: added method for randomly getting up to N seqs per sample