conda recipe for NeXus

[beenje]

Hello,
I created a conda recipe for NeXus that is now available on conda-forge: https://github.com/conda-forge/nexus-feedstock

This was based on the recipe used for mantid: https://github.com/mantidproject/conda-recipes/tree/master/nexus

I have no developer experience on windows. So the package is currently only for Linux and OSX. If someone is interested in adding windows support, please submit a PR.