add_rownames enhancement

[zhilongjia]

Currently, add_rownames add rownames as an explicit variable (default rowname). Can add_rownames or another function in dplyr add rownames for data.frame or tbl if there is a column named rowname or by assigning a column? This is a reverse operation of the current add_rownames. And actually add_rownames means add rownames for its literal meaning. Though dplyr wants no rowname for data.frame, it's necessary in many cases especially interacting with other packages in R. Usually I have to add the rowname, and delete the rowname column. It's related with #884. Thank you.

[hadley]

Moved to tibble.