Adding steps for setting up travis and appveyor (and some general notes)

CONTRIBUTING.md

@@ -26,6 +26,56 @@ to do this once to work on any of Facebook's open source projects.
 
 Complete your CLA here: <https://code.facebook.com/cla>
 
+## Setting up continuous integration (CI) on your fork
+Zstd uses a number of different continuous integration (CI) tools to ensure that new changes
+are well tested before they make it to an official release. Specifically, we use the platforms
+travis-ci, circle-ci, and appveyor.
+
+Changes cannot be merged into the main dev branch unless they pass all of our CI tests.
+The easiest way to run these CI tests on your own before submitting a PR to our dev branch
+is to configure your personal fork of zstd with each of the CI platforms. Below, you'll find
+instructions for doing this.
+
+### travis-ci
+Follow these steps to link travis-ci with your github fork of zstd
+
+1. Make sure you are logged into your github account
+2. Go to https://travis-ci.org/
+3. Click 'Sign in with Github' on the top right
+4. Click 'Authorize travis-ci'
+5. Click 'Activate all repositories using Github Apps'
+6. Select 'Only select repositories' and select your fork of zstd from the drop down
+7. Click 'Approve and Install'
+8. Click 'Sign in with Github' again. This time, it will be for travis-pro (which will let you view your tests on the web dashboard)
+9. Click 'Authorize travis-pro'
+10. You should have travis set up on your fork now.
+
+### circle-ci
+TODO
+
+### appveyor
+Follow these steps to link circle-ci with your girhub fork of zstd
+
+1. Make sure you are logged into your github account
+2. Go to https://www.appveyor.com/
+3. Click 'Sign in' on the top right
+4. Select 'Github' on the left panel
+5. Click 'Authorize appveyor'
+6. You might be asked to select which repositories you want to give appveyor permission to. Select your fork of zstd if you're prompted
+7. You should have appveyor set up on your fork now.
+
+### General notes on CI
+CI tests run every time a pull request (PR) is created or updated. The exact tests
+that get run will depend on the destination branch you specify. Some tests take
+longer to run than others. Currently, our CI is set up to run a short
+series of tests when creating a PR to the dev branch and a longer series of tests
+when creating a PR to the master branch. You can look in the configuration files
+of the respective CI platform for more information on what gets run when.
+
+Most people will just want to create a PR with the destination set to their local dev
+branch of zstd. You can then find the status of the tests on the PR's page. You can also
+re-run tests and cancel running tests from the PR page or from the respective CI's dashboard.
+
 ## Issues
 We use GitHub issues to track public bugs. Please ensure your description is
 clear and has sufficient instructions to be able to reproduce the issue.
@@ -34,7 +84,7 @@ Facebook has a [bounty program](https://www.facebook.com/whitehat/) for the safe
 disclosure of security bugs. In those cases, please go through the process
 outlined on that page and do not file a public issue.
 
-## Coding Style  
+## Coding Style
 * 4 spaces for indentation rather than tabs
 
 ## License