gloo: Apply appropriate glPixelStorei in 2D tex upload
gloo: Apply appropriate glPixelStorei in 2D tex upload

Closes issue #257

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