Add support for globs in exclusion

We've had numerous requests to support globs in our file/directory exclusion function.

There are several ways to handle this in light of our current exclusion functionality:

 - deprecate current functionality, implement globs in place. This will mean introducing incompatibility with current Bandit configurations.

 - support both with separate command flags - exclude_dirs works as it currently does and add exclude_globs. This is the least impactful way to add this functionality but means we're adding command flags and another config option.

 - try to squeeze globs and current path functionality into current exclusion mechanism. We could, for example, indicate a glob with a special character sequence. This seems hokey.