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.