Comment on different compilers in readme.rst.
Comment on different compilers in readme.rst.

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