prog_models v1.5.1

[teubert]

Release v1.5.1 Hotfix

Fixes two issues:

1. Issue where floating point errors can cause infinite loop when simulating using automatic step sizes and step size that cannot be divided evenly by two in floating point arithmetic.
2. Issue where None's in LSTM state cause array dtype to revert to object, which cannot be converted into a tensor.

---

This discussion was created from the release prog_models v1.5.1.