Added c++ dependency to .travis.yml

.travis.yml

@@ -1,6 +1,28 @@
 sudo: required
 language: cpp
-before_install: sudo apt-get update
+matrix:
+  include:
+    # works on Precise and Trusty
+    - os: linux
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+          packages:
+            - g++-6
+      env:
+        - MATRIX_EVAL="CC=gcc-6 && CXX=g++-6"
+
+    - os: osx
+      osx_image: xcode8
+      env:
+        - MATRIX_EVAL="brew install gcc && CC=gcc-6 && CXX=g++-6"
+
+before_install:
+  - sudo apt-get update
+  - eval "${MATRIX_EVAL}"
 install: ./install.sh
 script: ant test
 after_script: ./uninstall.sh
+after_success:
+  - bash <(curl -s https://codecov.io/bash)