feature/require-option

These two commits contain test cases and corresponding implementation for [Issue #78](https://github.com/benjaminoakes/maid/issues/78). I created a new branch named `feature/require-option` in my repo. (maybe I should merge it back to `master` locally first?)

Basically the new code requires specifying either `--noop` or `--execute` when running `maid clean`, otherwise a deprecation message is displayed.

If either option is present, it displays output based on if `--silent` is specified.

Running `maid clean --silent` will result in displaying the deprecation message as well.

Mu