Remove Cargo.lock from Git

[GabrielMajeri]

According to the Cargo book FAQ libraries should not check-in their Cargo.lock file.

[est31]

Thanks for your diligence! You are right, it's indeed the recommendation to not commit Cargo.lock into git. Let me explain why despite this, lewton still has a Cargo.lock.

Some time ago, I wanted to test how well some older rustc version was performing.
So I checked out some older version of my library, and tried to run the benchmark tool. Of the time when that older version was the most recent commit, this would have worked flawlessly. But since then, my Cargo.lock had been updated, and my dependencies needed newer rustc versions! This put me before a problem: I couldn't even test my own library! Sadly, Cargo doesn't have time travel support, nor does it resolve crates based on the required rustc version, skipping crates that need a too new rustc. I ended having to do a very laborious hack with cloning the index, checking out a commit from that time, and pointing cargo to be using it.

Until one of the two things (time travel support or MSRV used for resolution) is being supported for a long enough time, I think I'll keep Cargo.lock.