Plot BLAST Alignments

[Adamtaranto]

I'd like to add support for pre-computed alignments i.e. from BLAST, LASTZ, Minimap2, or Nucmer. Also mentioned in #5, addresses #12.

Logic for processing alignments is in flexidot.utils.matching func find_match_pos_diag() in PR #17

Options:

1. Take alignments in a simplified standard format rather than have Flexidot process multiple input formats. Allow users to handle filtering and formatting of alignments.

2. Add module to run alignment tool of choice on all pairwise combinations and generate standard alignment inputs.