fixes for bad minimal versions + checkout Cargo.lock

This commit fixes some of the bad minimal versions of the dependencies
we take, as well as checks out the `Cargo.lock` file (this is supposed
to be a library crate).

Author: connortsui20

.gitignore

@@ -3,10 +3,6 @@
 debug/
 target/
 
-# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
-# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
-Cargo.lock
-
 # These are backup files generated by rustfmt
 **/*.rs.bk