Release v2.6.0 - Githubissues

This is a PR to prep version 2.6.0 release of BioHansel.

Changes

bumped minor version
Added Rich for logging and informative tracebacks
refactoring and reformatting
fixed some docstrings
simplified some logic
replaced string.format with f-string literals
moved some functions to more appropriate places (e.g. degen sequence check functions from aho_corasick/__init__.py to utils.py)
moved check_total_kmers call to right after parsing of CLI args
replaced bio_hansel.parsers._parse_fasta with BioPython's Bio.SeqIO.FastaIO.SimpleFastaParser; forcing uppercase of sequence
cleaned up some tests
updated help message to show program name and version as well as nice list of built-in schemes
ignoring/fixed some warnings when pytest