Fix Travis-CI build. Closes #76

https://github.com/apache/logging-log4j2/pull/76 

.travis-toolchains.xml

+<?xml version="1.0" encoding="UTF8"?>
+<toolchains xmlns="http://maven.apache.org/TOOLCHAINS/1.1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/TOOLCHAINS/1.1.0 http://maven.apache.org/xsd/toolchains-1.1.0.xsd">
+  <toolchain>
+    <type>jdk</type>
+    <provides>
+      <id>java7</id>
+      <version>1.7</version>
+      <vendor>oracle</vendor>
+    </provides>
+    <configuration>
+      <jdkHome>/usr/lib/jvm/java-7-oracle</jdkHome>
+    </configuration>
+  </toolchain>
+  <toolchain>
+    <type>jdk</type>
+    <provides>
+      <id>java8</id>
+      <version>1.8</version>
+      <vendor>oracle</vendor>
+    </provides>
+    <configuration>
+      <jdkHome>/usr/lib/jvm/java-8-oracle</jdkHome>
+    </configuration>
+  </toolchain>
+  <toolchain>
+    <type>jdk</type>
+    <provides>
+      <id>java9</id>
+      <version>9</version>
+      <vendor>oracle</vendor>
+    </provides>
+    <configuration>
+      <jdkHome>/usr/lib/jvm/java-9-oracle</jdkHome>
+    </configuration>
+  </toolchain>
+</toolchains>
\ No newline at end of file

.travis.yml

@@ -11,10 +11,26 @@
 #   limitations under the License.
 
 language: java
-sudo: false
+# sudo enabled because sudo vms have more memory: https://docs.travis-ci.com/user/ci-environment/
+sudo: true
 
 jdk:
   - oraclejdk7
 
+env:
+  global:
+    JAVA_OPTS=-Xmx4g
+
+addons:
+  apt:
+    packages:
+      - oracle-java9-installer
+
+install:
+  - ./mvnw --toolchains=./.travis-toolchains.xml install -DskipTests=true -Dmaven.javadoc.skip=true -B -V
+
+script:
+  - ./mvnw --toolchains=./.travis-toolchains.xml test -B
+
 after_success:
-  - mvn --show-version -pl !log4j-bom jacoco:prepare-agent test jacoco:report coveralls:report
+  - ./mvnw --show-version -pl !log4j-bom jacoco:prepare-agent test jacoco:report coveralls:report
\ No newline at end of file