Remove non-ascii char in requirements.txt

Causes an error when running a build on readthedocs.org

requirements.txt

@@ -8,7 +8,7 @@ django-debug-toolbar==1.4.0
 django-extensions==1.6.1
 Werkzeug==0.9.6
 
-# Sandbox
+# Sandbox
 Whoosh==2.6.0
 pysolr==3.2.0
 requests==2.7.0