Migrate CI to GitHub Actions

- Remove travis ci configuration
- Add swiftlint step

Update parser combinator dependency

Remove MediaSegment equality function

Use the autogenerated equality function. This required fixing segment
name parsing. Previously the parser would return an empty string for
no name in an #EXTINF tag. Empty names should be nil instead. This was
not an issue because the equality function didn’t account for the
name.

Update Readme.md