add travis

.travis.yml

+language: java
+script:
+  - find . -type f -name "*.java" > sources.txt
+  - javac @sources.txt
+  
+notifications:
+    webhooks: https://www.travisbuddy.com/
+    on_success: never
+    on_failure: always
\ No newline at end of file

README.md

 # The Algorithms - Java
-
+[![Build Status](https://img.shields.io/travis/TheAlgorithms/Java.svg?label=Travis%20CI&logo=travis&style=flat-square)](https://travis-ci.com/TheAlgorithms/Java) 
 [![Donate](https://img.shields.io/badge/Donate-PayPal-green.svg)](https://www.paypal.me/TheAlgorithms/100)
 [![Gitter chat](https://img.shields.io/badge/Chat-Gitter-ff69b4.svg?label=Chat&logo=gitter&style=flat-square)](https://gitter.im/TheAlgorithms)