Disable surefire forking in Travis-CI

Attempt to fix build issues.

See: travis-ci/travis-ci#3396

Author: dhalperi

.travis.yml

@@ -9,29 +9,18 @@ notifications:
     on_success: change
     on_failure: always
 
-os:
-  - linux
-  - osx
-
-env:
-  matrix:
-    - CUSTOM_JDK="default"
-    - CUSTOM_JDK="oraclejdk8"
-    - CUSTOM_JDK="oraclejdk7"
-    - CUSTOM_JDK="openjdk7"
-
 matrix:
-  exclude:
-     # On OSX, run with default JDK only.
-     - os: osx
-       env: CUSTOM_JDK="oraclejdk8"
-     - os: osx
-       env: CUSTOM_JDK="oraclejdk7"
-     - os: osx
-       env: CUSTOM_JDK="openjdk7"
-     # On Linux, run with specific JDKs only.
-     - os: linux
-       env: CUSTOM_JDK="default"
+  include:
+    # On OSX, run with default JDK only.
+    - os: osx
+      env: MAVEN_OVERRIDE=""
+    # On Linux, run with specific JDKs only.
+    - os: linux
+      env: CUSTOM_JDK="oraclejdk8" MAVEN_OVERRIDE="-DforkCount=0"
+    - os: linux
+      env: CUSTOM_JDK="oraclejdk7" MAVEN_OVERRIDE="-DforkCount=0"
+    - os: linux
+      env: CUSTOM_JDK="openjdk7" MAVEN_OVERRIDE="-DforkCount=0"
 
 before_install:
   - if [ "$TRAVIS_OS_NAME" == "osx" ]; then export JAVA_HOME=$(/usr/libexec/java_home); fi
@@ -42,5 +31,5 @@ install:
 
 script:
   - travis_retry mvn versions:set -DnewVersion=manual_build
-  - travis_retry mvn install -U
+  - travis_retry mvn $MAVEN_OVERRIDE install -U
   - travis_retry travis/test_wordcount.sh