Fixes dead link in Readme. (#1969)

Author: MicahZoltu

README.md

@@ -61,4 +61,4 @@ OpenZeppelin is released under the [MIT License](LICENSE).
 [contribution guide]: CONTRIBUTING.md
 [Truffle]: https://truffleframework.com/docs/truffle/quickstart
 [Embark]: https://embark.status.im/docs/quick_start.html
-[Buidler]: https://buidler.dev/guides/#getting-started
+[Buidler]: https://buidler.dev/getting-started/#overview