fix some build issues

Fix travis issues in experimental branch

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

pom.xml

@@ -92,9 +92,10 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-javadoc-plugin</artifactId>
-                <version>2.10.4</version>
+                <version>3.1.0</version>
                 <configuration>
-                    <additionalparam>-Xdoclint:none</additionalparam>
+                    <doclint>none</doclint>
+                    <source>8</source>
                 </configuration>
                 <executions>
                     <execution>