Revert "Generate the overrides rather than relying on monkeypatching. Fixes #23"

This reverts commit 6b68e93ae80f0e0d4bbfcf3ed92db1dacc7ce66b.

There are bugs in the generator, and even accounting for those I haven't
succesfully gotten constraint overrides to work with this commit.
Reverting from master for now, will cherry pick into a
new_integration_method branch for future work and/or committing
back to master.