Varifier

Same as v0.3.0, except this has the correct version in the code, so `--version` does the right thing

* add option to not use maxmatch option with nucmer, for big genomes
* expose minimap2 and nucmer threads options
* improved handling of indels, in particular fixes a bug where FP indels could be called as TP, and also now uses current latest mummer version 4.0.0rc1 for better variant calls for recall.
* small bug fixes: handle whitespace in fasta header lines, non-ACGT characters, and lowercase characters

Backwards incompatible output compared to v0.1.0. Changes:

* added `--filter_pass` option to up front filter records in input VCF
* only reports one set of precision and recall, not filtered and unfiltered
* algorithm change to fix problem with clustered SNPs and indels. Was incorrectly calling TPs as FPs in cases where indels caused ref/probe alleles to not be aligned in the right place. Solved by applying all filtered variants to the probe flanks.

Initial release