Send coleslaw error output to stdout

I think Jenkins might fail my build because ‘coleslaw --help’ prints to stderr,
which it might interpret as errors. So I’m going to try printing help to stdout
instead.

Dockerfile

@@ -9,4 +9,4 @@ RUN curl -sL `curl -s https://api.github.com/repos/roswell/roswell/releases/late
 
 RUN ros install coleslaw-org/coleslaw
 ENV PATH="/root/.evm/bin:/root/.roswell/bin:$PATH"
-RUN coleslaw --help
+RUN coleslaw --help 2>&1