revert 1f8466164330277fc8c9126ded3cc207ff3baf91

Details: `RData` is a valid file format for bundling data with an R
package based on the "Writing R Extensions" manual:
http://cran.r-project.org/doc/manuals/r-release/R-exts.html#Data-in-packages
Merge pull request #1245 from daroczig/master

revert 1f8466164330277fc8c9126ded3cc207ff3baf91