Update contribution info in README.md (#379)

There is, since some time back, a dedicated 'contribute' page in a GitHub project, where good first issues are shown along with a link to the projects contribution guideline. I believe we should point our users there instead of directly to the contribution guidelines.

README.md

@@ -26,7 +26,7 @@ This repository contains the Eiffel protocol vocabulary, descriptions, guides an
 # About this repository
 The contents of this repository are licensed under the [Apache License 2.0](./LICENSE).
 
-To get involved, please see [Code of Conduct](https://github.com/eiffel-community/.github/blob/master/CODE_OF_CONDUCT.md) and [contribution guidelines](https://github.com/eiffel-community/.github/blob/master/CONTRIBUTING.md).
+To get involved, please see [Code of Conduct](https://github.com/eiffel-community/.github/blob/master/CODE_OF_CONDUCT.md) and our [contribution page](https://github.com/eiffel-community/eiffel/contribute).
 
 # About Eiffel
 This repository forms part of the Eiffel Community. Eiffel is a protocol for technology agnostic machine-to-machine communication in continuous integration and delivery pipelines, aimed at securing scalability, flexibility and traceability. Eiffel is based on the concept of decentralized real time messaging, both to drive the continuous integration and delivery system and to document it.