Follow R package conventions for directory structure

[claraqin]

The directory structure of this repository must be updated to match standard R package conventions before being made available to the public. The directories I suggest keeping are the following:

• R – to contain new R code, mainly utils.R
• man – to contain object documentation for the functions in utils.R
• vignettes – to contain all .Rmd vignettes

Where should params.R go?

Additional resources:

• http://www.mjdenny.com/R_Package_Pictorial.html
• https://r-pkgs.org/package-structure-state.html

[claraqin]

Potentially related:

• Ensuring that the installation of this package checks for the installation of all dependencies.
• Making this package compatible with devtools::install_github()

[claraqin]

https://tinyheero.github.io/jekyll/update/2015/07/26/making-your-first-R-package.html