Update to the latest lettuce and install from pypi

requirements/edx/base.txt

@@ -123,6 +123,7 @@ django-crum==0.5
 django_nose==1.2
 factory_boy==2.2.1
 freezegun==0.1.11
+lettuce==0.2.20
 mock==1.0.1
 nose-exclude
 nose-ignore-docstring

requirements/edx/github.txt

@@ -12,7 +12,6 @@
 -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-2#egg=django-oauth2-provider
 -e git+https://github.com/edx/MongoDBProxy.git@efe14679c9263ab491916ed960f5930127e05faf#egg=mongodb_proxy
--e git+https://github.com/gabrielfalcao/lettuce.git@cccc3978ad2df82a78b6f9648fe2e9baddd22f88#egg=lettuce
 -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