Replace invalid UTF-8 codepoints
Add a MANIFEST.in to get a complete sdist

In particular, we now include test data in sdist, so that it's possible
to run tests from the tarball that'd be uploaded on PyPI. This is useful
for distribution packaging where tests can be run during package build.

Also include LICENSE and README files along the way.
readme: add CI badge
ci: add .build.yml
readme: add command to execute tests
Ignore UTF-8 errors when decoding emails
Don't strip whitespace from lines
Make parse take a list of messages
Expand description in README
Establish proper Python module, add setup.py
Split into separate files
Rename to emailthreads
Fix matching split lines, add test with multiple replies
Use pytest for the test runner
Reverse matching, add test
Add a few basic tests
Remove scrubbed attachments footers
Change data structure to be a tree
Fix last block not parsed
Implement basic comments of comments