Remove the 2-argument inferReaderDriver

Per discussion in #336, this patch replaces the 2-argument version of `inferReaderDriver` with the 1-argument version. This is done over two commits since #336 included the first half of these changes.

@hobu note that the commit history is a bit funky between #336 and here. It should be ok to just straight up merge both into **master**, but a rebase of one of these two pull requests will make it all look nicer. If you merge one and want a cleaner history, let me know and I can do the rebase (well anyone can, but I'm happy to).