(#14) - pass verbose flag to tasks

Just as required by #14.

However:
1. if we run tasks which are not grunt's then `--verbose` can have side effects like command saying that it does not know such an option
2. if we run tasks which are grunt then's `--verbose` have side effect of showing its initialization steps twice. This is, however, not that bad.

Do you want to check if task is grunt's before passing the `--verbose` flag?