Remove travis badge in favor of circleci. (#578)

Author: jerjou

README.md

@@ -1,6 +1,5 @@
 # java-docs-samples
 
-[![Travis Build Status](https://travis-ci.org/GoogleCloudPlatform/java-docs-samples.svg?branch=master)](https://travis-ci.org/GoogleCloudPlatform/java-docs-samples)
 [![Circle-CI Build Status](https://circleci.com/gh/GoogleCloudPlatform/java-docs-samples.svg?style=shield&circle-token=117b41ead030b212fc7d519519ee9262c4f3480b)](https://circleci.com/gh/GoogleCloudPlatform/java-docs-samples)
 [![ghit.me](https://ghit.me/badge.svg?repo=GoogleCloudPlatform/java-docs-samples)](https://ghit.me/repo/GoogleCloudPlatform/java-docs-samples)
 [![Coverage Status](https://codecov.io/gh/GoogleCloudPlatform/java-docs-samples/branch/master/graph/badge.svg)](https://codecov.io/gh/GoogleCloudPlatform/java-docs-samples)