Standardize function documentation

[msleckman]

Standardize whether function doc strings sit before or after function body.

Great job on the documentation throughout. Typically doc for R functions sits outside the function body, rather than inside:

#' @description stuff here
#' @param a stuff here
#' @param b more stuff here

foo <- function(a, b) {
#even more stuff
}

Question for you - is it the other way in python?

Originally posted by @padilla410 in #16 (comment)