Slipcover

This release:
- fixes failing tests with Python 3.11;
- adds wheels for Python 3.11;
- adds an experimental option, `--immediate`, which essentially implements on-stack replacement by ignoring Python's rule that code objects should be immutable. Using it further reduces overhead, as Slipcover need not generate new code objects or update references to it. Use at your own risk... this is really only intended for research purposes;
- fixes an include file, ironically, not being included into the source distribution;

This release:
- fixes a bug causing Slipcover to move functions' docstrings when doing branch coverage, so that they could no longer be found;
- advances version to 0.2.0 given the support for branch coverage;

This release:
- adds branch coverage measuring support to slipcover; simply run it with `--branch` to get it.
- adds a "meta" item identify the source of the coverage information, as well as per-file and global summaries to the JSON output (issue 2).

This release:
- fixes a packaging issue omitting Python 3.11 from classifiers;
- acknowledges pypy support, contributed by cfbolz, and actually added in v0.1.7;

This release:
- adds support for Python 3.11 (technically 3.11.0b3);
- changes missing lines text formatting to include any non-code lines between missing ones, simplifying output and aligning it with Coverage.py;

Changes in this release:
- fixed file filter not being used for modules loaded through `pytest`, including uninteresting coverage results;
- simplified statistics gathering, also greatly improving its performance;