update contributing notes: DO NOT enable Circle for forks. (#3217)

* update contributing notes: DO NOT enable Circle for forks.

* finish the sentence

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,21 +1,20 @@
 #### Fixes #0000
 
 #### Checklist
-<!-- fill this section out if necessary, remove it otherwise -->
 
-- [ ] [Enable CircleCI for your fork](https://circleci.com/add-projects)
-- [ ] [Enable preview comments on CircleCI](https://github.com/palantir/blueprint/blob/develop/CONTRIBUTING.md#enable-preview-comments)
-- [ ] Include tests
+- [ ] Includes tests
 - [ ] Update documentation
 
+<!-- DO NOT enable CircleCI for your fork. Our build will run when you open this PR. -->
+
 #### Changes proposed in this pull request:
 
-<!-- fill this out -->
+<!-- Fill this out. -->
 
 #### Reviewers should focus on:
 
-<!-- fill this out -->
+<!-- Fill this out. -->
 
 #### Screenshot
 
-<!-- include an image of the most relevant user-facing change, if any -->
+<!-- Include an image of the most relevant user-facing change, if any. -->

CONTRIBUTING.md

@@ -41,28 +41,12 @@ A typical contributor workflow looks like this:
       `yarn lint` to be 100% safe.
     - TypeScript lint errors can often be automatically fixed by TSLint. Run lint fixes with `yarn lint-fix`.
 1. Submit a Pull Request on GitHub and fill out the template.
+    - ⚠️ __DO NOT enable CircleCI for your fork of Blueprint.__ Our build
+      will run on your fork when you open a PR. You can run NPM scripts locally
+      to validate before pushing code.
 1. Team members will review your code and merge it after approvals.
     - You may be asked to make modifications to code style or to fix bugs you may have not noticed.
     - Please respond to comments in a timely fashion (even if to tell us you need more time).
     - _Do not_ amend commits and `push --force` as they break the PR history. Please add more commits; we squash each PR to a single commit on merge.
 1. Hooray, you contributed! :tophat:
 
-### Enable preview comments
-
-The team relies on PR "preview comments" for immediate feedback on features during development.
-Forkers must manually enable comments by defining the `GH_AUTH_TOKEN` environment variable on
-CircleCI.
-
-If you're developing on a fork of Blueprint:
-
-1. Navigate to [CircleCI](https://circleci.com/add-projects), log in using your GitHub account,
-and click **"Build project"** for your fork of Blueprint.
-1. Navigate to the [token settings](https://github.com/settings/tokens) on GitHub and create a user
-token with the `public_repo` scope.
-1. Navigate to your CircleCI repo settings: `https://circleci.com/gh/<username>/blueprint/edit#env-vars`
-and create a new environment variable called `GH_AUTH_TOKEN` with the token you created earlier.
-The end result should look like so:
-
-    ![image](https://cloud.githubusercontent.com/assets/464822/22609529/6845d7e6-ea16-11e6-8a8e-444057bc4687.png)
-1. When a build passes, a comment will be automatically posted to your PR that links to the
-generated artifacts containing your changes.