chore(travis): Whitelist greenkeeper branches (JamesHenry#6)

Author: greenkeeper[bot]

.travis.yml

@@ -16,4 +16,5 @@ after_success:
   - yarn semantic-release
 branches:
   only:
-    - master
+    - master
+    - /^greenkeeper/.*$/

README.md

@@ -13,4 +13,6 @@
 <p align="center" style="border: 1px solid blue;">
 <a href="http://typescriptcourses.com" target="_blank"><img src="https://user-images.githubusercontent.com/900523/33187671-54d039fc-d08b-11e7-809b-b5b99b5a8a8f.png" alt="typescriptcourses.com"/></a>
 </p>
-<br>
+<br>
+
+[![Greenkeeper badge](https://badges.greenkeeper.io/JamesHenry/eslint-plugin-tslint.svg)](https://greenkeeper.io/)