use this horrible complex bit of shell to make sure that curl doesn't hand the poor user a broken docker client

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)

docs/sources/installation/mac.rst

@@ -65,11 +65,12 @@ Run the following commands to get it downloaded and set up:
 
 .. code-block:: bash
 
-    # Get the file
-    curl -o docker https://get.docker.io/builds/Darwin/x86_64/docker-latest
-
-    # Mark it executable
-    chmod +x docker
+    # Get the docker client file
+    DIR=$(mktemp -d) && \
+    curl -f -o $DIR/ld.tgz https://get.docker.io/builds/Darwin/x86_64/docker-latest.tgz && \
+    gunzip $DIR/ld.tgz && \
+    tar xvf $DIR/ld.tar -C $DIR/ && \
+    cp $DIR/usr/local/bin/docker ./docker
 
     # Set the environment variable for the docker daemon
     export DOCKER_HOST=tcp://127.0.0.1:4243