Clear up README

[gowerc]

The README example code keeps getting out of date and confusing people. We could switch to Rmd to ensure it runs but honestly given the complexity of the package I think I'd prefer to just remove it and point people to the vignette instead.

[gowerc]

@gravesti - Any objects before I implement this ?

[gravesti]

@gowerc Nope, that sounds good to me. Would you keep the intro and installation sections?