Consider if DataDeps were Paths.

[oxinabox]

Note that right now:
joinpath(datadep"a", "b") and datadep"a/b" are different.

and the later is preferred because it does recovery if files are missing.
and if #35 eventuates it will become even more so.

It might be better to use https://github.com/rofinn/FilePathsBase.jl
and have the thing returned by datadep"a" be a path.
and also on those lines maybe have it not make it download immediaty when resolved, but rather when files within it are accessed.

This is really DataDeps 2.0 stuff, and not something I want to work on immediately,
but might be good the think on.