ipynb app: dont use glut as a back-backend
ipynb app: dont use glut as a back-backend

This should prevent the stalling of Travis I hope

kkuunnddaannkk/vispy,sh4wn/vispy,srinathv/vispy,RebeccaWPerry/vispy,inclement/vispy,jay3sh/vispy,QuLogic/vispy,dchilds7/Deysha-Star-Formation,michaelaye/vispy,Eric89GXL/vispy,sbtlaarzc/vispy,sh4wn/vispy,jay3sh/vispy,Eric89GXL/vispy,kkuunnddaannkk/vispy,RebeccaWPerry/vispy,dchilds7/Deysha-Star-Formation,bollu/vispy,inclement/vispy,ghisvail/vispy,hronoses/vispy,sbtlaarzc/vispy,dchilds7/Deysha-Star-Formation,sh4wn/vispy,kkuunnddaannkk/vispy,drufat/vispy,inclement/vispy,jdreaver/vispy,michaelaye/vispy,julienr/vispy,bollu/vispy,hronoses/vispy,julienr/vispy,ghisvail/vispy,bollu/vispy,drufat/vispy,michaelaye/vispy,drufat/vispy,ghisvail/vispy,jdreaver/vispy,srinathv/vispy,RebeccaWPerry/vispy,jay3sh/vispy,QuLogic/vispy,julienr/vispy,jdreaver/vispy,QuLogic/vispy,srinathv/vispy,hronoses/vispy,Eric89GXL/vispy,sbtlaarzc/vispy