Updated links in readme.rst.
Updated links in readme.rst.

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