Use a forked version of NLTK

So that we can use setuptools instead of distribute

common/lib/chem/setup.py

@@ -8,6 +8,6 @@ setup(
         "pyparsing==2.0.1",
         "numpy",
         "scipy",
-        "nltk==2.0.5",
+        "nltk<3.0",
     ],
 )

requirements/edx-sandbox/base.txt

@@ -8,5 +8,7 @@ numpy==1.6.2
 networkx==1.7
 sympy==0.7.1
 pyparsing==2.0.1
-nltk==2.0.5
 matplotlib==1.3.1
+
+# We forked NLTK just to make it work with setuptools instead of distribute
+-e git+https://github.com/edx/nltk.git@2.0.6#egg=nltk

requirements/edx/base.txt

@@ -53,7 +53,6 @@ meliae==0.4.0
 mongoengine==0.7.10
 MySQL-python==1.2.5
 networkx==1.7
-nltk==2.0.5
 nose==1.3.3
 oauthlib==0.7.2
 paramiko==1.9.0

requirements/edx/github.txt

@@ -13,6 +13,7 @@
 -e git+https://github.com/edx/django-wiki.git@cd0b2b31997afccde519fe5b3365e61a9edb143f#egg=django-wiki
 -e git+https://github.com/edx/django-oauth2-provider.git@0.2.7-fork-edx-5#egg=django-oauth2-provider
 -e git+https://github.com/edx/MongoDBProxy.git@25b99097615bda06bd7cdfe5669ed80dc2a7fed0#egg=mongodb_proxy
+-e git+https://github.com/edx/nltk.git@2.0.6#egg=nltk
 -e git+https://github.com/dementrock/pystache_custom.git@776973740bdaad83a3b029f96e415a7d1e8bec2f#egg=pystache_custom-dev
 -e git+https://github.com/eventbrite/zendesk.git@d53fe0e81b623f084e91776bcf6369f8b7b63879#egg=zendesk
 -e git+https://github.com/un33k/django-ipware.git@42cb1bb1dc680a60c6452e8bb2b843c2a0382c90#egg=django-ipware