split up travis build into 3 build matrix slots

.travis.yml

@@ -1,6 +1,11 @@
 language: cpp
 
-before_script:
+env:
+   - variant=test_debug
+   - variant=test_release
+   - variant=test_barebones
+
+install:
    - if [ $TRAVIS_OS_NAME == linux ]; then sudo add-apt-repository -y ppa:boost-latest/ppa; sudo apt-get update -qq; fi
    - if [ $TRAVIS_OS_NAME == linux ]; then sudo apt-get install libboost1.54-all-dev python2.7-dev; fi
    - if [ $TRAVIS_OS_NAME == osx ]; then sudo brew install boost boost-build python27-dev; fi
@@ -12,16 +17,11 @@ before_script:
 
 script:
    - cd test
-   - bjam -j2 warnings=off -l900 $CC
-   - bjam -j2 variant=test_debug warnings=off -l900 $CC
+   - bjam -j2 variant=$variant warnings=off -l900 $CC
    - cd ../examples
-   - bjam -j2 variant=test_debug warnings=off $CC
-   - bjam -j2 variant=test_barebones warnings=off $CC
-   - bjam -j2 variant=test_release warnings=off $CC
+   - bjam -j2 variant=$variant warnings=off $CC
    - cd ../bindings/python
-   - bjam -j2 variant=test_debug warnings=off $CC
-   - bjam -j2 variant=test_barebones warnings=off $CC
-   - bjam -j2 variant=test_release warnings=off $CC
+   - bjam -j2 variant=$variant warnings=off $CC
 
 compiler:
    - gcc