added closeall for gr/pyplot

src/Plots.jl

@@ -67,6 +67,7 @@ export
     savefig,
     png,
     gui,
+    closeall,
 
     backend,
     backends,

src/backends/gr.jl

@@ -1079,3 +1079,5 @@ function _display(plt::Plot{GRBackend})
         gr_display(plt)
     end
 end
+
+closeall(::GRBackend) = GR.emergencyclosegks()

src/backends/pyplot.jl

@@ -1224,3 +1224,5 @@ for (mime, fmt) in _pyplot_mimeformats
         )
     end
 end
+
+closeall(::PyPlotBackend) = PyPlot.plt[:close]("all")

src/output.jl

@@ -172,6 +172,8 @@ for mime in keys(_mimeformats)
     end
 end
 
+closeall() = closeall(backend())
+
 
 # ---------------------------------------------------------
 # A backup, if no PNG generation is defined, is to try to make a PDF and use FileIO to convert