Create a PR adding roave/backward-compatibility-check similar to previous PRs for adding other composer based tools, include tests, entry in the tools section for the tool and a link to the repo at the bottom of the README like other tools.

Create a PR adding roave/backward-compatibility-check similar to previous PRs for adding other composer based tools, include tests, entry in the tools section for the tool and a link to the repo at the bottom of the README like other tools. #4