Regsister fsspec interface with fsspec

The following stackoverflow question brought to my attention that, although this repo has an fsspec-compatible class, it is not registered with fsspec, so calls like fsspec.open("gdrive://...") don't work. Even importing the library does not seem to do the registration. (They DO work with the older gdrivefs.)

We should figure out what the appropriate protocol to use is and make sure that users have as smooth a path as possible to loading data off gdrive via fsspec.