Travis test

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index 9c733f5..13e110e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,15 +6,17 @@
   
 # Enable C++ support
 language: cpp
-addons:
-  apt:
-    sources:
-      - ubuntu-toolchain-r-test
-    packages:
-      - gcc-6
-      - g++-6
-      - cmake
 
+matrix: 
+   - os: linux
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+          packages:
+            - g++-6
+      env:
+        - MATRIX_EVAL="CC=gcc-6 && CXX=g++-6"
 
 # Compiler selection
 compiler: