defer to xdg-open on remaining platforms

lib/open.js

@@ -1,4 +1,5 @@
 var exec = require('child_process').exec;
+var path = require('path');
 
 
 /**
@@ -21,12 +22,12 @@ function open(target, callback) {
       break;
     default:
       // use xdg open everywhere else
-      throw Error('Platform "' + process.platform + '" is not supported yet');
+      opener = path.join(__dirname, '../vendor/xdg-open');
       break;
   }
 
   // TODO: what are the implications of quoting target?
-  // on windows things go wrong... 
+  // on windows things go wrong...
   // for instance 'start "http://www.google.com"' fails by opening a new
   // instance of cmd.exe
   return exec(opener + ' ' + target + '', callback);