Pyodesys

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- OdeSys.integrate* methods now return a tuple: (xout, yout, info-dict)
currently there are no guarantees about the exact contents of the info-dict.
- signature of callbacks of rhs and jac in OdeSys are now:
(t, y_arr, param_arr) -> f_arr
- two new methods: adaptive and predefined (incl. tests)
- Support roots
- Refactor plot_result (interpolation now available)
- Make Matrix class optional
- Added force_predefined kwarg to integrate()
- Fix bug in symmetricsys().from_callback()
- New upstream versions of pyodeint, pycvodes and pygslodeiv2
- Tweak tests of pycvodes backend for new upstream
- New example

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- New OdeSys class factory: symmetricsys for symmetric transformations
- Breaking change (for consistency with symneqsys): (lband, uband) -> band
- New convenience method: OdeSys.plot_result

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- added util.check_transforms

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- Variable transformations supported
- Only require sympy, numpy and scipy in requirements.txt

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- support for scipy, pyodeint, pygslodeiv2, pycvodes