Use GOption instead of popt

See [gnome docs](http://library.gnome.org/devel/libgnome/stable/libgnome-gnome-program.html#gnome-program-init).  popt is deprecated, we need to start using GOption.  Needs to be changed around [main.c:39](https://github.com/dwest/grip/blob/master/src/main.c#L39) and [main.c:164](https://github.com/dwest/grip/blob/master/src/main.c#L164)
