Actually release v0.7.0

[RandomInsano]

Things are a bit stuck at the moment. I've locked the embedded-hal library to exactly 0.2.2 to avoid warnings about using deprecated functions until the Linux Embedded HAL catches up (I hit some problems with passing a None:: into the constructor there.

I'm also stuck due to a library problem between nix and libc that may require me to either backport/freeze some libraries or to wait until every dependency that requires the three different versions of the nix crate are satisfied.

The big change that embedded folks will depend on is in #16. For now, I think they'll have to rely on using this Git repository directly instead of Crates.io.

[RandomInsano]

Nix has been updated! I just need to run some tests to make sure everything is looking good and the ball can get rolling.