Get rid of stdin for deis config:push

[pfeodrippe]

The implementation of deis config:push here uses stdin to fetch the buffer, but it was causing me problems as you can see at this issue. Running the command inside a script which gets its inputs from stdin, I had to pipe it with < dev/null to get the correct result or it would give me Creating config... ...Error: Unknown Error (409): {"detail":"user changed nothing - release stopped"}.

Can something be made to correct it?

[Joshua-Anderson]

Looks like we need to switch code to check if a filename is provided before attempting to use stdin.

[Cryptophobia]

This issue was moved to teamhephy/workflow-cli#6