win: Make sure shell.showItemInFolder in called on browser side.

Fixes #341.

atom/common/api/lib/clipboard.coffee

@@ -1,5 +1,5 @@
 module.exports =
-  if process.platform is 'linux'
+  if process.platform is 'linux' and process.__atom_type is 'renderer'
     # On Linux we could not access clipboard in renderer process.
     require('remote').process.atomBinding 'clipboard'
   else

atom/common/api/lib/shell.coffee

@@ -1 +1,4 @@
 module.exports = process.atomBinding 'shell'
+
+if process.platform is 'win32' and process.__atom_type is 'renderer'
+  module.exports.showItemInFolder = require('remote').process.atomBinding('shell').showItemInFolder