factor out getting the users arg; make createsliver only handle 1 rspec
factor out getting the users arg; make createsliver only handle 1 rspec

tcmitchell/geni-tools,GENI-NSF/gram,plantigrade/geni-tools,GENI-NSF/gram,ahelsing/geni-tools,GENI-NSF/gram,tcmitchell/geni-tools,plantigrade/geni-tools,ahelsing/geni-tools