Added tendermint/testing docker image description

DOCKER/Dockerfile.testing

@@ -0,0 +1,18 @@
+FROM golang:1.10.1
+
+
+# Grab deps (jq, hexdump, xxd, killall)
+RUN apt-get update && \
+  apt-get install -y --no-install-recommends \
+  jq bsdmainutils vim-common psmisc netcat
+
+# Add testing deps for curl
+RUN echo 'deb http://httpredir.debian.org/debian testing main non-free contrib' >> /etc/apt/sources.list && \
+  apt-get update && \
+  apt-get install -y --no-install-recommends curl
+
+VOLUME /go
+
+EXPOSE 46656
+EXPOSE 46657
+

DOCKER/Makefile

@@ -7,6 +7,9 @@ push:
 build_develop:
 	docker build -t "tendermint/tendermint:develop" -f Dockerfile.develop .
 
+build_testing:
+	docker build --tag tendermint/testing -f ./Dockerfile.testing .
+
 push_develop:
 	docker push "tendermint/tendermint:develop"