In autogenerated _version file, use full Git hash

The `codetools/_version.py` file (which is autogenerated by the `setup` script) should use the full Git commit hash instead of the abbreviated 7-hex version. It currently looks like this:
```
mirzakhani:codetools mdickinson$ cat codetools/_version.py
# THIS FILE IS GENERATED FROM CODETOOLS SETUP.PY
version = '4.3.0'
full_version = '4.3.0'
git_revision = 'c2a0c1b'
is_released = True

if not is_released:
version = full_version
```