Implement `node-debug` script

Add a CLI script `node-debug` that:
 1. Runs node-inspector.
 2. Runs the supplied script in debug mode or starts a REPL session
 3. Opens the user's browser, pointing it at the inspector.

Add a CLI script `run-repl` (used by `node-debug`) that will load
the module in CWD and start a REPL session.

The script `node-debug` is friendly to embedders, error messages use the value of the env variable "CMD" when referring to $0.

/to: @sam-github please review. I'll submit the documentation changes in a standalone pull request.

The file node-debug.js is based on [strong-cli/lib/commands/debug.js](https://github.com/strongloop/strong-cli/blob/master/lib/commands/debug.js). The most notable difference is the naming of command-line arguments. I have decided to use the names that are already used by Node and Node Inspector (e.g. `--web-port` instead of `--port`, `--debug-brk` instead of `--suspend`). I have added aliases to keep backwards compatibility with `slc debug`.

/cc: @sidorares @Krxtopher @jfirebaugh
The script `node-debug` added by this pull request is replacing your modules [ni](https://github.com/sidorares/ni), [node-ndebug](https://github.com/resource/node-ndebug) and [node-debug](https://github.com/jfirebaugh/node-debug). Is there any feature that is implemented in your module and missing in node-inspector's node-debug?