Add missing build_docker.sh

docker/build_docker.sh

+set -x
+set -e
+set -u
+
+BUILD_NAME=0.5.1
+
+for type in pyston pyston-numpy; do
+    for tag in latest ${BUILD_NAME}; do
+        cd ~/pyston/docker/${type}
+        # "docker build" only recently gained the ability to take multiple -t flags
+        docker build -t pyston/${type}:latest ~/pyston/docker/${type}
+        docker build -t pyston/${type}:${BUILD_NAME} ~/pyston/docker/${type}
+    done
+done
+
+for type in pyston pyston-numpy; do
+    for tag in latest ${BUILD_NAME}; do
+        cd ~/pyston/docker/${type}
+        docker push pyston/${type}:latest
+        docker push pyston/${type}:${BUILD_NAME}
+    done
+done