Update TVGuide Parsing

[shadow578]

fixes parsing issues described in #32 .

additionally updates the way that the episode-num field is parsed, with added test cases.

[codecov]

Codecov Report

Attention: Patch coverage is 96.77419% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
custom_components/xmltv_epg/model/guide.py	50.00%	1 Missing ⚠️
custom_components/xmltv_epg/model/program.py	96.15%	1 Missing ⚠️

Files with missing lines	Coverage Δ
custom_components/xmltv_epg/api.py	72.22% <100.00%> (ø)
test/model/test_TVProgram.py	100.00% <100.00%> (ø)
custom_components/xmltv_epg/model/guide.py	88.88% <50.00%> (-2.29%)	⬇️
custom_components/xmltv_epg/model/program.py	93.10% <96.15%> (+1.16%)	⬆️