Q2-itsxpress

* This release adds support for the output of unmerged trimmed reads for use by Dada2. The new command is now available as`trim-pair-output unmerged`
* Documentation has been updated.

Fixed the interleaved problem.

Fix for issue validating fastq.gz files

Changed the default clustering identity to 99.5% for increased accuracy.

* Versioning is now tied to the versioning of ITSxpress
* This release adds a new feature to cluster merged sequences at less than 100% identity. This speeds up typical dataset trimming by about 10x over previous versions depending on the sample, without major effects on trimming accuracy. This feature is controlled with the --cluster_id flag. Default behavior is now to cluster at 0.987 identity.

* Test data is now included in MANIFEST.in
* Cleanup of documentation