heyoka 0.4.0

This new release of heyoka comes with several new features:

• support for outputting the Taylor coefficients that were used to perform a single time step,
• support for dense (continuous) output,
• efficient propagation over a time grid via dense output,
• new automatic simplifications in the expression system,
• a new function powi() for exponentiation with natural exponents.

There is also an important bugfix regarding a division by zero in certain corner cases when using pow() with small natural exponents.

As usual, the full changelog is available here:

https://bluescarni.github.io/heyoka/changelog.html