added build status to readme
added build status to readme

samuelshaner/openmc,lilulu/openmc,mjlong/openmc,paulromano/openmc,kellyrowland/openmc,bhermanmit/openmc,shikhar413/openmc,johnnyliu27/openmc,smharper/openmc,mit-crpg/openmc,walshjon/openmc,amandalund/openmc,shikhar413/openmc,walshjon/openmc,smharper/openmc,paulromano/openmc,walshjon/openmc,liangjg/openmc,liangjg/openmc,wbinventor/openmc,smharper/openmc,mit-crpg/openmc,wbinventor/openmc,samuelshaner/openmc,mit-crpg/openmc,johnnyliu27/openmc,lilulu/openmc,johnnyliu27/openmc,wbinventor/openmc,walshjon/openmc,samuelshaner/openmc,mjlong/openmc,shikhar413/openmc,amandalund/openmc,amandalund/openmc,samuelshaner/openmc,kellyrowland/openmc,lilulu/openmc,smharper/openmc,mit-crpg/openmc,paulromano/openmc,shikhar413/openmc,wbinventor/openmc,amandalund/openmc,liangjg/openmc,bhermanmit/openmc,paulromano/openmc,liangjg/openmc,johnnyliu27/openmc