Bug fixes, odeint API & features, support for python 3.7
- Added the ability to explicitly pass parameters in the form of a dictionary at each ODE solver step
- fixed_odeint can now accept dictionaries as state
- added save_at argument to odeint to have the solver save the solution only at specified time instants
- Data control variable u in NeuralODE has been changed to _control
- Added support for Python 3.7
- various bug fixes