Try to read rds formatted files #227
Description
When reading data that has been pinned in the rds format, right now users get an error. However, there are tools out there that can read in tabular data that has been pinned as rds.
We should suggest users install rdata or other package (have it as an optional dependency?) if they try to read an rds file. If it is installed, we will try to convert it automatically. Not all rds pins will be able to be converted (say, models are not compatible), so we'll want reasonable errors as well if it cannot be read.