Merge pull request #47 from dario23/master

README.rst: make example compile

Author: tailhook

README.rst

@@ -129,7 +129,7 @@ You may add multiple options for the same variable::
 
 Similarly positional arguments are added::
 
-    let mut command = String;
+    let mut command = String::new();
     parser.refer(&mut command)
         .add_argument("command", Store,
                       "Command to run");