Consider a cost limit for in-memory cache as well as disk cache

[jacobjennings]

Really great work @jstn, very much appreciated, thanks for sharing. I think that a cost limit would be useful for the in-memory cache just as well as the disk cache. Was the omission a design choice?

[jstn]

Thanks! Not a design choice per se, just not something we've needed yet at Tumblr. It's a great idea though, I'll do it.

[jstn]

This has been added in 1.0.1