Change installation message

src/backends/glvisualize.jl

@@ -77,14 +77,9 @@ end
 
 function add_backend_string(b::GLVisualizeBackend)
     """
-    For those incredibly brave souls who assume full responsibility for what happens next...
-    There's an easy way to get what you need for the GLVisualize backend to work (until Pkg3 is usable):
-
-    Pkg.clone("https://github.com/tbreloff/MetaPkg.jl")
-    using MetaPkg
-    meta_checkout("MetaGL")
-
-    See the MetaPkg readme for details...
+    if !Plots.is_installed("GLVisualize")
+        Pkg.add("PyPlot")
+    end
     """
 end