Added `faux` under testing libraries

faux is a library to create mocks out of structs. 

I did the PR by following the [requested format](https://github.com/rust-unofficial/awesome-rust/blob/master/CONTRIBUTING.md) but it doesn't match most of the existing listed libraries so let me know if I should make them match the existing libraries instead of the format under the contributing guidelines.

README.md

@@ -672,6 +672,7 @@ See also [Are we (I)DE yet?](https://areweideyet.com/) and [Rust Tools](https://
 * [laboratory](https://crates.io/crates/laboratory) — A simple, expressive unit test framework for Rust ![build](https://github.com/enokson/laboratory/workflows/build/badge.svg?branch=master)
 * [cucumber-rust](https://crates.io/crates/cucumber-rust) — An implementation of the Cucumber testing framework for Rust. [![Build Status](https://github.com/bbqsrc/cucumber-rust/workflows/CI/badge.svg?branch=master)](https://github.com/bbqsrc/cucumber-rust)
 * [demonstrate](https://crates.io/crates/demonstrate) — Declarative Testing Framework [![Build Status](https://github.com/austinsheep/demonstrate/workflows/Continuous%20Integration/badge.svg?branch=master)](https://github.com/austinsheep/demonstrate)
+* [nrxus/faux](https://github.com/nrxus/faux/) [![Latest Version](https://img.shields.io/crates/v/faux.svg)](https://crates.io/crates/faux) — A library to create mocks out of structs. ![build](https://github.com/nrxus/faux/workflows/test/badge.svg?branch=master)
 * [httpmock](https://github.com/alexliesenfeld/httpmock) — HTTP mocking [![build badge](https://dev.azure.com/alexliesenfeld/httpmock/_apis/build/status/alexliesenfeld.httpmock?branchName=master)](https://dev.azure.com/alexliesenfeld/httpmock/_build/latest?definitionId=2&branchName=master)
 * [mockiato](https://crates.io/crates/mockiato) — A strict, yet friendly mocking library for Rust 2018 [![build badge](https://api.travis-ci.com/mockiato/mockiato.svg?branch=master)](https://travis-ci.com/mockiato/mockiato)
 * [mutagen](https://crates.io/crates/mutagen) — A source-level mutation testing framework (nightly only) [![build badge](https://api.travis-ci.org/llogiq/mutagen.svg?branch=master)](https://travis-ci.org/llogiq/mutagen)