Use LRU cache in rudimentary ways

[Moelf]

Probably for 2.0 release or something but I ran into some very light / nice implementation for example https://github.com/marius311/Memoization.jl .

I realized uproot4 has dropped the way-too-many kinds of cache so we probably should learn from Jim in making one here. I think a good start would be to at leach cache whole branch / tree if they fit, in case users are doing some small exploration work.

For the larger-than-RAM TChain like event loop, cache is less useful:

1. user probably is running a script (so a one-off thing)
2. LRU cache is useless since accessed elements are >> RAM size.

[tamasgal]

Thanks Jerry, LRU is definitely on the feature-list and Memoization.jl looks definitely nice!

Yes, indeed, uproot4 massively simplified the caching, we should definitely go that path ;)

[tamasgal]

Let's put it in v1 (hopefully in 2020)

[Moelf]

closed by #24, now we cache decompressed basketbytes based on (ROOTFile, branch, ith_basket)
https://github.com/tamasgal/UnROOT.jl/blob/ce28568b4c054afee02d323f7c4d96b56aff580e/src/root.jl#L240