add CLA link to Contributing (#222)

* add CLA link to Contributing

* adds CLA link to PR template

* adds note about re-running CLA check

* updates welcome to include links

.github/PULL_REQUEST_TEMPLATE.md

@@ -30,3 +30,4 @@ Fixes # (issue)
 - [ ] I have added tests that prove my fix is effective or that my feature works
 - [ ] New and existing unit tests pass locally with my changes
 - [ ] The test coverage did not decrease
+- [ ] I have signed the appropriate [Contributor License Agreement](https://cla.shopify.com/)

.github/welcome.yml

@@ -2,7 +2,7 @@ newIssueWelcomeComment: >
   Thanks for opening your first issue here! Be sure to follow the issue template!
 
 newPRWelcomeComment: >
-  Thanks for opening this pull request! Please check out our contributing guidelines and sign the CLA.
+  Thanks for opening this pull request! Please check out our [contributing guidelines](https://github.com/Shopify/kubeaudit#contribute) and [sign the CLA](https://cla.shopify.com/).
 
 firstPRMergeComment: >
   Congrats on merging your first pull request, keep em coming!

README.md

@@ -718,6 +718,9 @@ If you'd like to fix a bug, contribute a feature or just correct a typo, please
 1. Run the tests to see everything is working as expected: `make test`
 1. Commit your changes: `git commit -am 'Adds awesome feature'`
 1. Push to the branch: `git push fork`
+1. Sign the [Contributor License Agreement](https://cla.shopify.com/)
 1. Submit a PR (All PR must be labeled with :bug: (Bug fix), :sparkles: (New feature), :book: (Documentation update), or :warning: (Breaking changes) )
 1. ???
 1. Profit
+
+Note that if you didn't sign the CLA before opening your PR, you can re-run the check by adding a comment to the PR that says "I've signed the CLA!"!