Adding names to NAMESPACE

It turns out that, while you only need a blank NAMESPACE file to install the package, it needs names in it for the functions to work!  I've added them here.

I'm considering doing a little work on this package to make it easier for others to contribute in the future (converting documentation to Roxygen, breaking up the file structure, etc.)  I'm thinking about this because I get a lot of people in D-RUG who use your package but have version issues because they took the class a previous year, or got it from another student who did.  I figure plenty of these students will be using your functions as they move to new projects/jobs, and I think these few changes will make the package easier to maintain over the long term.  Let me know if you'd be interested in this.