refs #35: set default icon on windows.

Signed-off-by: Eric Wang <skygragon@gmail.com>

Author: skygragon

lib/icon.js

@@ -12,7 +12,8 @@ var icons = {
 };
 
 icons.setTheme = function(name) {
-  var theme = this.themes[name] || this.themes.default || {};
+  var defaultName = process.platform === 'win32' ? 'win7' : 'default';
+  var theme = this.themes[name] || this.themes[defaultName] || {};
   _.extendOwn(this, theme);
 };