Version bump to 3.1.0 and changed to git

Dockerfile

@@ -19,7 +19,7 @@ FROM tier/shibboleth_sp
 ARG registry=docker.io
 ARG maintainer=tier
 ARG imagename=comanage
-ARG version=2.0.0
+ARG version=3.1.0
 ARG tierversion=17040
 
 MAINTAINER $maintainer
@@ -73,7 +73,7 @@ ENV COMANAGE_URL=https://github.com/Internet2/comanage-registry/archive/$VERSION
 ENV COMANAGE_PREFIX=comanage-registry
 
 RUN mkdir -p /tmp/comanage && cd /tmp/comanage && \
-      wget -q $COMANAGE_URL && \
+      git clone -b feature-3.1 https://github.com/Internet2/comanage-registry.git && \
 # Perform verifications [TODO]
 # Prepare filesystem
       mkdir -p /opt/comanage && \