Added instructions to README on how to run the spec tests.

README.rst

@@ -67,6 +67,11 @@ nose_ works great! ::
     cd pystache
     nosetests --with-doctest
 
+To include tests from the mustache spec_ in your test runs: ::
+
+    git submodule init
+    git submodule update
+
 
 Mailing List
 ==================
@@ -90,4 +95,5 @@ Author
 .. _et: http://www.ivan.fomichev.name/2008/05/erlang-template-engine-prototype.html
 .. _Mustache: http://defunkt.github.com/mustache/
 .. _mustache(5): http://mustache.github.com/mustache.5.html
-.. _nose: http://somethingaboutorange.com/mrl/projects/nose/0.11.1/testing.html
\ No newline at end of file
+.. _nose: http://somethingaboutorange.com/mrl/projects/nose/0.11.1/testing.html
+.. _spec: https://github.com/mustache/spec