dockeri does not accept container/image arguments

[chbrandt]

When containers have their own set of arguments we want dockeri redirecting them to the container itself.

Consider the following case:

# dockeri -w /tmp/workdir image:tag --opt bla arg1 arg2

We are asking docker to run the container image:tag (with -v /tmp/workdir:/work), and options --opt bla arg1 arg2 will be used internally by the container; dockeri should not parse those options.

[chbrandt]

Related to issue #3