Add the ability to test wasm and fixes a few linter errors

[s0l0ist]

This library can be compiled to WASM, but supporting testing for that target doesn't work out of the box. This PR addresses that.

While testing wasm, the compiler reported a few linter errors and would fail to compile (due to the project config). I've fixed them:

• Unnecessary qualified TryFrom
• Recommended to use serde-wasm-bindgen

How to test WASM

Install wasm-pack

Run the test command. I'm using the --release flag for speed and opting to use node (which expects a node to be in the environment). Running in the browser can be configured with more code changes, but using node should be sufficient for local testing. Unfortunately, the wasm target only works with the rust or crypto feature as gmp or openssl do not support wasm targets:

• wasm-pack test --node --release --no-default-features --features wasm,rust
• wasm-pack test --node --release --no-default-features --features wasm,crypto or the shorter command wasm-pack test --node --release --features wasm

Results:

[INFO]: ⬇️  Installing wasm-bindgen...
    Finished release [optimized] target(s) in 0.04s
     Running unittests src/lib.rs (target/wasm32-unknown-unknown/release/deps/libpaillier-db39394c44027fb1.wasm)
no tests to run!
     Running tests/paillier.rs (target/wasm32-unknown-unknown/release/deps/paillier-965e043a1c0af98c.wasm)
Set timeout to 20 seconds...
running 7 tests                                   

test paillier::test_all ... ok
test paillier::test_proof ... ok
test paillier::test_bytes ... ok
test paillier::test_serialization ... ok
test paillier::test_mul ... ok
test paillier::test_add ... ok
test paillier::test_encrypt ... ok

test result: ok. 7 passed; 0 failed; 0 ignored; 0 filtered out

[mikelodder7]

The faster/slower is a little misleading. crypto backend is all constant time vs rust which is not. If you are managing secrets its preferred to use crypto as your backend. However, since this is all browser based it might not make much of a difference. Thanks for the PR. reviewing

[s0l0ist]

Understood, I've removed the verbiage from the PR body for future readers. What I was trying to say is that enabling the crypto feature runs slower than the rust feature when running the tests for the WASM target.