- added support for `vsearch` for pre-processing reads as well as mapping reads to OTUs. If `vsearch` is installed, scripts will use it automatically, otherwise default to Python and/or usearch
- fix bug in `ufits filter` that resulted in error if no index bleed filter or spike in barcode passed on argument line
- also a home-brew formula to install ufits. `brew tap nextgenusfs/tap` followed by `brew install ufits` will install the package as well as `bedtools` and `vsearch` two optional dependencies. `usearch` must still be installed manually.