Update to v0.3 of Embark's standard lints

[XAMPPRocky]

Embark uses a standard set of lints across all repositories. We just upgraded
to version 0.3 of these lints, and this repository needs to be updated to
the new set of lints with any warnings fixed.

Steps

1. Copy the contents of the lints.rs file from
   EmbarkStudios/rust-ecosystem and replace the old list of lints in the
   src/lib.rs and/or src/main.rs files with the new list.
2. Run cargo clippy
3. Update and fix any code that now triggers a new warning.

[emilk]

Closed in #21