Use correct Python wrapper package for magic

See http://stackoverflow.com/a/12297929

requirements.txt

@@ -9,7 +9,6 @@ lxml==3.2.4
 nose==1.3.0
 pyparsing==2.0.1
 python-daemon==1.6
-python-magic==0.4.6
 pytz==2013.8
 requests==2.0.1
 simplejson==3.3.1
@@ -21,3 +20,4 @@ xlrd==0.9.2
 WebOb==1.1.1
 WebTest==1.4.2
 cssselect==0.9.1
+-e git+https://github.com/mammadori/magic-python.git#egg=Magic_file_extensions