Merge pull request #1461 from shaneknapp/fix-broken-contrib-roadmap-link

fix broken links in `CONTRIBUTING.md`

Author: rgaiacs

CONTRIBUTING.md

@@ -5,23 +5,23 @@
 (And thank you particularly for coming to read the guidelines! :heart_eyes:)
 
 The repo2docker developer documentation is all rendered on our documentation website: [https://repo2docker.readthedocs.io](https://repo2docker.readthedocs.io).
-If you're here, you're probably looking for the [Contributing to repo2docker development](https://repo2docker.readthedocs.io/en/latest/contributing/contributing.html) page.
+If you're here, you're probably looking for the [Contributing to repo2docker development](https://repo2docker.readthedocs.io/en/latest/contribute/contributing.html) page.
 
 Please make sure you've read the following sections before opening an issue/pull request:
 
-- [Process for making a contribution](https://repo2docker.readthedocs.io/en/latest/contributing/contributing.html#process-for-making-a-contribution).
+- [Process for making a contribution](https://repo2docker.readthedocs.io/en/latest/contribute/contributing.html#process-for-making-a-contribution).
   - These steps talk you through choosing the right issue template (bug report or feature request) and making a change.
-- [Guidelines to getting a Pull Request merged](https://repo2docker.readthedocs.io/en/latest/contributing/contributing.html#guidelines-to-getting-a-pull-request-merged).
+- [Guidelines to getting a Pull Request merged](https://repo2docker.readthedocs.io/en/latest/contribute/contributing.html#guidelines-to-getting-a-pull-request-merged).
   - These are tips and tricks to help make your contribution as smooth as possible for you and for the repo2docker maintenance team.
 
 There are a few other pages to highlight:
 
-- [Our roadmap](https://repo2docker.readthedocs.io/en/latest/contributing/roadmap.html)
+- [Our roadmap](https://repo2docker.readthedocs.io/en/latest/contribute/roadmap.html)
   - We use the roadmap to develop a shared understanding of the project's vision and direction amongst the community of users, contributors, and maintainers.
     This is a great place to get a feel for what the maintainers are thinking about for the short, medium, and long term future of the project.
 - [Design of repo2docker](https://repo2docker.readthedocs.io/en/latest/design.html)
   - This page explains some of the design principles behind repo2docker.
     Its a good place to understand _why_ the team have made the decisions that they have along the way!
   - We absolutely encourage discussion around refactoring, updating or extending repo2docker, but please make sure that you've understood this page before opening an issue to discuss the change you'd like to propose.
-- [Common developer tasks and how-tos](https://repo2docker.readthedocs.io/en/latest/contributing/tasks.html)
+- [Common developer tasks and how-tos](https://repo2docker.readthedocs.io/en/latest/contribute/tasks.html)
   - Some notes on running tests, buildpack dependencies, creating a release, and keeping the pip files up to date.