Finaletoolkit

Fixed
- update docs, docstring, and help message for wps to mention that
`site_bed` must be sorted.

Added
- `normalize` keyword argument and `--normalize` flag to
`finaletoolkit.frag.coverage` function and `finaletoolkit coverage` subcommand,
respectively. Setting this argument/flag to true results in the output
being normalized by the total coverage, ignoring `scale_factor` if specified.
- `--intersect-policy` or `-p` flag added to `finaletoolkit coverage`subcommand.

Fixed
- subpackages can now be accessed when importing `finaletoolkit`. Previously,
the following code resulted in an error:
python
>>> import finaletoolkit as ftk
>>> help(ftk.frag)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: module 'finaletoolkit' has no attribute 'frag'

Now this is a valid way to access subpackages `cli`, `frag`, `genome`, and
`utils`.

Fixed
- indexing issue in region_end_motifs that would misread strand
information when calculating end motifs on forward-strand only.

Changed
- frag_generator now accepts fragment coordinates in bed.gz files

Fixed
- `delfi` accepts `gap_file=None`
- update prog for `delfi` to reflect compatibility with reference genomes
other than hg19

Changed
- Added many tests for util functions

Fixed
- Changed a nopython function to use numba compatible indexing

Changed
- Used "not" instead of "~" in an if statement
- Added a test for the coverage function

Fixed
- Ensured that the coverage value returns the expected value (previously
returned an empty generator)