Change sudo pip2 to just pip3 in readme

Author: JakeRoggenbuck

README.rst

@@ -35,15 +35,15 @@ To install for normal usage:
 
 .. code-block:: bash
 
-    sudo pip2 install mechanize
+    pip3 install mechanize
 
 To install for development:
 
 .. code-block:: bash
 
     git clone https://github.com/python-mechanize/mechanize.git
     cd mechanize
-    sudo pip2 install -e .
+    pip3 install -e .
 
 To install manually, simply add the `mechanize` sub-directory somewhere on your
 `PYTHONPATH`.