electrum: enable plotting support

Plotting seems to be a core feature now, with a menu entry available by
default. Without the matplotlib dependency this opens a warning popup
though.

pkgs/applications/misc/electrum/default.nix

@@ -13,6 +13,7 @@ python2Packages.buildPythonApplication rec {
     dns
     ecdsa
     jsonrpclib
+    matplotlib
     pbkdf2
     protobuf
     pyaes
@@ -30,7 +31,6 @@ python2Packages.buildPythonApplication rec {
     # TODO plugins
     # amodem
     # btchip
-    # matplotlib
   ];
 
   preBuild = ''