New clippy errors with Rust 1.53

[thanethomson]

I was busy preparing the v0.20.0 release when I discovered that it looks like a bunch of new clippy warnings have been introduced in Rust 1.53. These cause our clippy checks to fail since we fail on warnings.

Steps to reproduce

1. Update to Rust 1.53
2. Run the following:

cargo clippy --all-features --all-targets -- -Dwarnings -Drust-2018-idioms

You should get output resembling the following:

error: used `assert_eq!` with a literal bool
  --> proto/tests/unit.rs:66:5
   |
66 |     assert_eq!(new_domain_type.part_set_header_exists, false);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `assert!(..)`
   |
   = note: `-D clippy::bool-assert-comparison` implied by `-D warnings`
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#bool_assert_comparison

error: methods with the following characteristics: (`to_*` and `self` type is `Copy`) usually take `self` by value
   --> tendermint/src/public_key.rs:159:21
    |
159 |     pub fn to_bytes(&self) -> Vec<u8> {
    |                     ^^^^^
    |
note: the lint level is defined here
   --> tendermint/src/lib.rs:9:5
    |
9   |     warnings,
    |     ^^^^^^^^
    = note: `#[deny(clippy::wrong_self_convention)]` implied by `#[deny(warnings)]`
    = help: consider choosing a less ambiguous name
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#wrong_self_convention

...

What's the definition of "done" for this issue?

When clippy, using Rust 1.53, gives us no errors.