update python version in windows instructions

content/install.rst

@@ -283,7 +283,7 @@ provided by Christoph Gohlke.  To install Kwant on Windows
 1. Determine whether you have a 32-bit or 64-bit Windows installation by
    following these `instructions <http://support.microsoft.com/kb/827218>`_.
 
-2. Download and install Python 2.7 for the appropriate architecture (32-bit or
+2. Download and install Python 3.4 for the appropriate architecture (32-bit or
    64-bit) from the official `Python download site
    <http://www.python.org/download/>`_.
 
@@ -292,11 +292,11 @@ provided by Christoph Gohlke.  To install Kwant on Windows
 
 4. In the command prompt window, execute::
 
-        C:\Python27\python.exe C:\Python27\Tools\Scripts\win_add2path.py
+        C:\Python34\python.exe C:\Python34\Tools\Scripts\win_add2path.py
 
    (Instead of typing this command, you can also just copy it from here and
    paste it into the command prompt window). If you did not use the default
-   location to install Python in step 2, then replace ``C:\Python27`` by the
+   location to install Python in step 2, then replace ``C:\Python34`` by the
    actual location where Python is installed.
 
 5. Reboot your computer.