Add CHANGELOG.md, update it for 3.0 major release (plaid#123)

Author: skylarmb

CHANGELOG.md

@@ -0,0 +1,9 @@
+## 3.0.0
+- Adds support for `/sandbox/item/set_verification_status`
+- `PaymentRecipientAddress` can now be null
+- Removed support for deprecated `/item/access_token/update_version` endpoint
+
+BREAKING CHANGES:
+
+- Removed `client.UpdateAccessTokenVersion`
+- `PaymentRecipientAddress` can now be null

PUBLISH.md

@@ -13,7 +13,9 @@ git pull origin master
 git fetch --tags
 ```
 
-3. Creating a new release is simple and bundled into a single make command. Use
+3. Create and merge a PR to update `CHANGELOG.md`
+
+4. Creating a new release is simple and bundled into a single make command. Use
 semantic versioning to determine whether a release should be one of the follow
 version bumps:
 - `patch`