added ipython installation into travis CI
added ipython installation into travis CI

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