handle ijulia with requires

and properly check if juno/ijulia are actually used and not just loaded

src/Plots.jl

@@ -245,8 +245,6 @@ function __init__()
     # for compatibility with Requires.jl:
     @init
 
-    setup_ijulia()
-
     if isdefined(Main, :PLOTS_DEFAULTS)
         for (k,v) in Main.PLOTS_DEFAULTS
             default(k, v)

src/output.jl

@@ -250,12 +250,11 @@ end
 
 const _ijulia_output = String["text/html"]
 
-function setup_ijulia()
-    # override IJulia inline display
-    if isijulia()
-        @eval begin
-            import IJulia
+using Requires
+@require IJulia begin
+    if IJulia.inited
         export set_ijulia_output
+
         function set_ijulia_output(mimestr::AbstractString)
             # info("Setting IJulia output format to $mimestr")
             global _ijulia_output
@@ -270,17 +269,18 @@ function setup_ijulia()
         function Base.show(io::IO, m::MIME"text/plain", plt::Plot)
             show(io, MIME("text/html"), plt)
         end
-        end
-        @eval set_ijulia_output("text/html")
+
+        set_ijulia_output("text/html")
     end
 end
 
 # ---------------------------------------------------------
 # Atom PlotPane
 # ---------------------------------------------------------
-using Requires
 @require Juno begin
     import Hiccup, Media
+
+    if Juno.isactive()
         Media.media(Plot, Media.Plot)
 
         function Juno.render(e::Juno.Editor, plt::Plot)
@@ -318,3 +318,4 @@ using Requires
             Juno.render(pane, HTML(s))
         end
     end
+end