Added some documentation about testing with docker

tests/README.md

@@ -0,0 +1,47 @@
+# Automated Testing Documentation
+
+## To Create Test Environment Container
+
+From the root of the repository:
+
+    docker build --rm=false \
+        -t steemitinc/ci-test-environment:latest \
+        -f tests/scripts/Dockerfile.testenv .
+
+## To Run The Tests
+
+(Also in the root of the repository.)
+
+    docker build --rm=false \
+        -t steemitinc/steem-test \
+        -f Dockerfile.test .
+
+## To Troubleshoot Failing Tests
+
+    docker run -ti \
+        steemitinc/ci-test-environment:latest \
+        /bin/bash
+
+Then, inside the container:
+
+(These steps are taken from `/Dockerfile.test` in the
+repository root.)
+
+    git clone https://github.com/steemit/steem.git \
+        /usr/local/src/steem
+    cd /usr/local/src/steem
+    git checkout <branch> # e.g. 123-feature
+    git submodule update --init --recursive
+    mkdir build
+    cd build
+    cmake \
+        -DCMAKE_BUILD_TYPE=Debug \
+        -DBUILD_STEEM_TESTNET=ON \
+        -DLOW_MEMORY_NODE=OFF \
+        -DCLEAR_VOTES=ON \
+        ..
+    make -j$(nproc) chain_test
+    ./tests/chain_test
+    cd /usr/local/src/steem
+    doxygen
+    programs/build_helpers/check_reflect.py