Tracking Revert of PR #37

[thearossman]

(Since AFAIK Github doesn't let you re-open a merged and reverted PR)

I just reverted #37 (#37) because it broke compilation on ARM machines. Details are here: #41

I worked on this for a bit and couldn't find a relatively quick fix (e.g., replacement library with same API) -- we'd need to find a different library with equivalent functionality.

@sippejw tagging you so that you're aware this got reverted! As I think you're the primary one using these extra rust-crypto features, there's no rush to fix it. I can also get to it at some point.

[sippejw]

PR #55 removes the deprecated dependency and replaces it with aes-gcm which is actively maintained.