update one URL to please R-devel CMD check

Author: eddelbuettel

README.md

@@ -78,9 +78,10 @@ Released and tested versions of Rcpp are available via the
 install.packages("Rcpp")
 ```
 
-To install from source, ensure you have a 
-[complete package development environment](http://www.rstudio.com/ide/docs/packages/prerequisites). 
-Also see questions 1.2 and 1.3 in the [Rcpp-FAQ](http://cran.r-project.org/web/packages/Rcpp/vignettes/Rcpp-FAQ.pdf).
+To install from source, ensure you have a
+[complete package development environment](https://support.rstudio.com/hc/en-us/articles/200486498-Package-Development-Prerequisites).
+Also see questions 1.2 and 1.3 in the
+[Rcpp-FAQ](http://cran.r-project.org/web/packages/Rcpp/vignettes/Rcpp-FAQ.pdf).
 
 ### Authors