Update README.md with proper grammar

Past tense of "run" is "ran", not "runned".

README.md

@@ -555,7 +555,7 @@ Then, you can run the test with:
 
 ### Browser tests
 
-Browser tests are not included in `npm test` as they run for too long, although they are runned automatically on Travis when merged into master. Run browser tests locally in any browser:
+Browser tests are not included in `npm test` as they run for too long, although they are ran automatically on Travis when merged into master. Run browser tests locally in any browser:
 
     $ npm run test-browser-local