Support guide column callback function

This allows a config function to be registered
in the atom.coffee file to support different wrap
guide columns depending on the type of file being
viewed.

src/app/root-view.coffee

@@ -97,10 +97,10 @@ class RootView extends View
       when 'PaneColumn' then PaneColumn.deserialize(viewState, this)
       when 'Editor' then Editor.deserialize(viewState, this)
 
-  activateExtension: (extension) ->
+  activateExtension: (extension, config) ->
     throw new Error("Trying to activate an extension with no name") unless extension.name?
     @extensions[extension.name] = extension
-    extension.activate(this, @extensionStates[extension.name])
+    extension.activate(this, @extensionStates[extension.name], config)
 
   deactivateExtension: (extension) ->
     extension.deactivate?()

src/app/window.coffee

@@ -61,9 +61,9 @@ windowAdditions =
     unless $("head style[id='#{id}']").length
       $('head').append "<style id='#{id}'>#{text}</style>"
 
-  requireExtension: (name) ->
+  requireExtension: (name, config) ->
     extensionPath = require.resolve name
-    extension = rootView.activateExtension require(extensionPath)
+    extension = rootView.activateExtension(require(extensionPath), config)
 
     extensionKeymapPath = fs.join(fs.directory(extensionPath), "keymap.coffee")
     require extensionKeymapPath if fs.exists(extensionKeymapPath)