Added a test for wms layer.
Added a test for wms layer.

zhoujh30/folium,themiurgo/folium,shankari/folium,python-visualization/folium,python-visualization/folium,ocefpaf/folium,kod3r/folium,QuLogic/folium,xujun10110/folium,kod3r/folium,talespaiva/folium,shankari/folium,zhoujh30/folium,BibMartin/folium,ozak/folium,koldunovn/folium,BibMartin/folium,themiurgo/folium,talespaiva/folium,themiurgo/folium,droythorne/folium,andrewgiessel/folium,QuLogic/folium,koldunovn/folium,droythorne/folium,BibMartin/folium,shankari/folium,ozak/folium,zhoujh30/folium,koldunovn/folium,droythorne/folium,ozak/folium,andrewgiessel/folium,talespaiva/folium,LACMTA/folium,LACMTA/folium,andrewgiessel/folium,xujun10110/folium,xujun10110/folium,LACMTA/folium,ocefpaf/folium,QuLogic/folium,talespaiva/folium,kod3r/folium