ParmEd Error with AmberTools ==20.0

[SimonBoothroyd]

The new version of ambertools ==20.0 seems to have broken compatibility with openmoltools.

In particular, the version number of the ParmEd which ships with the new ambertools seems to be incorrect.

ambertools = 20.0: parmed at20RC5+54.g5702a232fe.dirty pypi_0 pypi

ambertools = 19.11: parmed 3.2.0 pypi_0 pypi

which yields the following exception:

# If ParmEd is older than 2.0.4 then halt - newer ParmEd is required to have correct FudgeLJ/FudgeQQ retained in GROMACS topologies.
    try:
        ver = parmed.version
    except:
        oldParmEd = Exception('ERROR: ParmEd is too old, please upgrade to 2.0.4 or later')
        raise oldParmEd
    if ver < (2,0,4):
>       raise RuntimeError("ParmEd is too old, please upgrade to 2.0.4 or later")
E       RuntimeError: ParmEd is too old, please upgrade to 2.0.4 or later

cc @jaimergp

[jchodera]

This is fixed in #274. I'll cut a new release now.

[jchodera]

cc https://github.com/conda-forge/ambertools-feedstock/issues/35