Add setuptools config, set up versioneer

[mcwitt]

• Adds project setup.py, adapted from https://github.com/pypa/sampleproject/blob/main/setup.py
• Adds configuration for versioneer to handle versioning based on git tags (set up following instructions here)
• Builds C++ lib with setuptools. Notes:
  • current method using make build still works
  • default CUDA_ARCH is now defined in CMakeLists.txt (as opposed to Makefile)
• Changes the default CUDA_ARCH to 75 (this is what we're using in ansible builds)
• Updates setup instructions

Versioning

Currently we get

>>> import timemachine as tm
>>> tm.__version__
'0+untagged.642.gda016b2'

After tagging, e.g.

git tag -a 0.1.0

we'll get

>>> tm.__version__
'0.1.0'

After the next (untagged) commit, it'll look like

>>> tm.__version__
'0.1.0+1.g7ac99fd'

[mcwitt]

Dev and testing dependencies can be installed via pip install .[dev] or pip install .[test] respectively.

[mcwitt]

Force-pushed to remove some local configuration I had accidentally committed.

[mcwitt]

Unfortunately these exclusions need to be duplicated here from pyproject.toml (unless we want to use force-exclude, which would prevent any invocation of black from formatting these files; see psf/black#438)

[mcwitt]

Without this I get

CMake Error at CMakeLists.txt:32 (add_subdirectory):
  add_subdirectory not given a binary directory but the given source
  directory
  ...
  When specifying an out-of-tree source a binary directory must be explicitly
  specified.

[mcwitt]

This is to allow pip install . to succeed without needing to first set e.g. CMAKE_ARGS="-DCUDA_ARCH=75"

[mcwitt]

Moving this to draft status as there are still a few issues to work out with the setuptools build.

[mcwitt]

The default CUDA_ARCH setting was moved to CMakeLists.txt. This will allow pip install -e . to succeed without needing to set the CMake flags.

[maxentile]

These seem like great changes. Tested out the updated instructions for installing in develop mode and it all worked as expected. (Also quite nice to be able to access timemachine.__version__ from within a script!)