add recipes for specifying a different gulpfile and setting a different base path using plain JS - closes #122

There is no need for custom logic to specify a custom `gulpfile` or set a custom base.  It can be done with vanilla node.

If `--gulpfile` is still desired, this can be remove when it is implemented, but I don't think it is too much boilerplate.  Especially because you can remove the `try/catch` and just let it error on failure to find the file or directory.