Fix for issue #92

[flacoste]

I've added three tests:

• One demonstrates that subcommands work with repl() - there was no such test.
• The other two demonstrates the issue documented in #92.

Not sure yet on how to make them pass, welcoming any ideas.

[flacoste]

After investigation, I realized that calling the group() command on every subcommand is part of click's expected behavior so it should be preserved. Once it's known, it's still possible to take advantage of the group context caching. The fix for the arguments is to use group.invoke() to make the dispatch by passing the new args in the context.

[GhostOps77]

Hi @flacoste , any updates on making these test cases?