We actually only need to skip VLSpec validation but not Vg. Also improve the suffix check.  (This should be faster than the old condition and regexp)
We actually only need to skip VLSpec validation but not Vg.
Also improve the suffix check.  (This should be faster than the old condition and regexp)

cc: da39a3ee5e6b4b0d3255bfef95601890afd80709@arvind

uwdata/vega-lite,uwdata/vega-lite,vega/vega-lite,uwdata/vega-lite,uwdata/vega-lite,uwdata/vega-lite,vega/vega-lite,vega/vega-lite,vega/vega-lite,vega/vega-lite