fix some build issues

I have no idea if this project is dead but it seems some build
issues need fixing so this is my first pass at doing so.

Author: snecklifter

.travis.yml

@@ -1,19 +1,19 @@
 sudo: required
+services:
+  - xvfb
 language: java
 
 jdk:
-  - oraclejdk8
-  - oraclejdk9
-  - openjdk7
+  - oraclejdk11
+  - openjdk8
+  - openjdk11
 
 before_install:
   - sudo apt-get -qq update
   - sudo apt-get build-dep libjlatexmath-java
 
 before_script:
   - "export DISPLAY=:99.0"
-  - "sh -e /etc/init.d/xvfb start"
-  - sleep 3 # give xvfb some time to start
 
 after_success:
   - mvn cobertura:cobertura coveralls:report