disabled the pre-filter by default
updated default parameters for uclust-based OTU pickers. fixes #1585
fixed error
fixed bug in test
added link to peerj preprint
fixed formatting
fixed typo
fixed merge conflicts
fixed typo
updated tutorial to reflect publication of PeerJ PrePrint, and to generally bring up-to-date
updated description of reference
updated discussion of parameters file
removed description of fast uclust parameters
fixed over-indentation
fixed soem typos
Merge pull request #1586 from gregcaporaso/issue-1585

updates to OTU picking parameter defaults