added a couple tests for GLVertexData
added a couple tests for GLVertexData

taylorhxu/tangram,ceseale/tangram,taylorhxu/tangram,DHaylock/tangram,zerebubuth/tangram,rosamcgee/tangram,ceseale/tangram,xvilan/tangram,DHaylock/tangram,TitoAgudelo/tangram,DHaylock/tangram,taylorhxu/tangram,tangrams/tangram,ceseale/tangram,xvilan/tangram,TitoAgudelo/tangram,zerebubuth/tangram,zerebubuth/tangram,xvilan/tangram,rosamcgee/tangram,TitoAgudelo/tangram,rosamcgee/tangram,tangrams/tangram