Remove `apt-get upgrade` from dockerfile per best practices.
@@ -3,9 +3,7 @@ MAINTAINER MIT Probabilistic Computing Project
ARG check_args
-RUN apt-get update -qq \
- && apt-get upgrade -qq \
- && apt-get install -qq -y \
+RUN apt-get update -qq && apt-get install -qq -y \
git \
python-apsw \
python-jsonschema \
