clarified HDF5 installation
clarified HDF5 installation

nhorelik/openmc,amandalund/openmc,johnnyliu27/openmc,amandalund/openmc,mit-crpg/openmc,smharper/openmc,walshjon/openmc,kellyrowland/openmc,mjlong/openmc,smharper/openmc,amandalund/openmc,liangjg/openmc,lilulu/openmc,liangjg/openmc,samuelshaner/openmc,sxds/opemmc,lilulu/openmc,bhermanmit/cdash,sxds/opemmc,lilulu/openmc,wbinventor/openmc,paulromano/openmc,johnnyliu27/openmc,amandalund/openmc,kellyrowland/openmc,mit-crpg/openmc,wbinventor/openmc,mjlong/openmc,mit-crpg/openmc,johnnyliu27/openmc,paulromano/openmc,mit-crpg/openmc,shenqicang/openmc,liangjg/openmc,liangjg/openmc,johnnyliu27/openmc,wbinventor/openmc,smharper/openmc,shikhar413/openmc,walshjon/openmc,walshjon/openmc,samuelshaner/openmc,walshjon/openmc,shikhar413/openmc,bhermanmit/openmc,nhorelik/openmc,paulromano/openmc,samuelshaner/openmc,shenqicang/openmc,paulromano/openmc,wbinventor/openmc,shikhar413/openmc,shikhar413/openmc,bhermanmit/openmc,samuelshaner/openmc,smharper/openmc