ODEBench non-importable; DEMO notebook therefore does not work

[MMathisLab]

Dear @sdascoli, first thanks for this great work; we are excited to build on it.

We noticed in testing your work that your ODEBench module has no init file, thus is not part of the `pypi' package, and therefore your demo notebook was not runnable "as is," for me.

A simple fix is an __init__.py file, which I add in this PR: #16

I can confirm it works now:

• pip from my fork:

Results:

[sdascoli]

Thanks, just merged the PR!
Excited to hear what you’re up to 😃