Improve command line interface and help

[neckhair]

When I first tried running this project I only got an error "Fatal Error, no deployment defined". This was confusing because the help command did not say anything about a deployment. Also this error message seems to come from deep within the checking code.

A more helpful implementation would define required CLI arguments as required and show them in the help message like this:

USAGE:
   livelint check [command options] <deployment>

I was digging a little through the docs of the CLI framework we're using and did not find an automatic way to define an argument as required. But there is an option to show the arguments in the help output (ArgsUsage).

Maybe we can discuss replacing this framework with Cobra, which does these things a little better and also helps with separating the commands into different files. But maybe there are arguments for the one we're using too.

[qasimwarraich]

Thanks, @neckhair! I have taken this feedback into account in the new UI feature branch @cldmstr and I have started.

Output to livelint and livelint c now appear as so: