Intronic

BUGFIX: `intronIC` now correctly handles cases where, using BED-format input, putatively-misannotated U12-type introns are identified and have their coordinates adjusted. Previously, this triggered a GTF/GFF-centric subroutine to adjust annotated exon/CDS coordinates based on the new intron coordinates, which threw an error when running with BED input.

- BUGFIX: BED output start coordinates are now (correctly) 0-indexed rather than 1-indexed (thanks MichaelHiller)
- New arg `--no_nc_ss_adjustment` disables the default heuristic for detecting putatively-misannotated U12-type introns by the presence of a strong U12-like 5′SS near the annotated start site of non-canonical introns.

Include `networkx` as a dependency in `setup.cfg`, where it should have been all along.

Fix annoying issues with generating a version number under different installation scenarios.

- Deal with edge-case issue where a `gene` feature has children
`exon`/`CDS` features in a direct parent-child relationship.
Previously, this would bypass the recursive search for introns used
by `get_introns()` due to an early exit, resulting in preferential
inclusion of introns whose `Parent` attribute was the gene itself
rather than a child transcript.
- Remove old code/fix whitespace
- Update `__version__` paradigm
- Remove _Physarum_-specific branch-point PWM code

Misc. minor changes not affecting functionality.

Switch to limiting `master` (soon to be `main`) to point releases, with development code contained to `dev`.