added download instructions for CRAN

Author: btskinner

README.md

@@ -6,7 +6,13 @@
 This package is meant to facilitate working with the [U.S. Department of Education College Scorecard](https://collegescorecard.ed.gov) data in R. It is a wrapper
 for the Scorecard API that uses piped commands a la [`dplyr`](http://github.com/hadley/dplyr) to convert idiomatic R synax into the correct url format.
 
-Download the development version with
+Install the latest released version from CRAN with
+
+```{r}
+install.packages('rscorecard')
+```
+
+Install the latest development version from Github with
 
 ```{r}
 devtools::install_github('btskinner/rscorecard')