Travis yaml update

Author: robbievanleeuwen

.travis.yml

@@ -1,10 +1,33 @@
 language: python
+
 before_install:
   - pip install pybind11
-python:
-  - "3.5"
-  - "3.6"
+
+matrix:
+  include:
+    - os: linux
+      compiler: gcc
+      addons: &gcc49
+        apt:
+          sources: ['ubuntu-toolchain-r-test']
+          packages: ['g++-4.9', 'gcc-4.9']
+      env:
+        - CXX='g++-4.9'
+        - CC='gcc-4.9'
+      python: 3.5
+    - os: linux
+      compiler: gcc
+      addons: &gcc49
+        apt:
+          sources: ['ubuntu-toolchain-r-test']
+          packages: ['g++-4.9', 'gcc-4.9']
+      env:
+        - CXX='g++-4.9'
+        - CC='gcc-4.9'
+      python: 3.6
+
 install:
   - python setup.py install
+
 script:
-  - python ./sectionproperties/tests/tests/test_rectangle.py
+  - python ./sectionproperties/tests/test_rectangle.py