API: added method for randomly getting up to N seqs per sample
Add numerical entry box for rarefaction depth
Delete hacky code

Fixes #246
REL: scikit-bio dep
Add rarefaction to biom table generation

Right now this is analysis-wide, but some day it should be per-datatype...
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
Change minimum rarefaction depth to 10
Merge pull request #255 from wasade/random_subset_seqs

API: added method for randomly getting up to N seqs per sample
Add sanity checking to rarefaction_depth
Add tests for sanity-checking
Merge pull request #256 from adamrp/select_rarefaction_depth

Select rarefaction depth