feat: Real docker-based testing

This pull request switches testing to use an actual docker daemon, vs mocking everything out.

It may also catch actual breaking issues in our tests, which is great!

help-functions

@@ -41,7 +41,7 @@ fn-help-all() {
       return "$?"
     fi
 
-    echo -e "${BOLD}usage${NORMAL}: dokku $PLUGIN_COMMAND_PREFIX[:COMMAND]"
+    echo -e "${BOLD}usage${NORMAL}: dokku ${PLUGIN_COMMAND_PREFIX}[:COMMAND]"
     echo ''
     echo -e "${BOLD}List your $PLUGIN_COMMAND_PREFIX services.${NORMAL}"
     echo ''