Try and fix Travis C++11 support (clang+gcc)

.travis.yml

@@ -1,13 +1,56 @@
+# http://genbattle.bitbucket.org/blog/2016/01/17/c++-travis-ci/
+
+# Ubuntu 14.04 Trusty support
+sudo: required
+dist: trusty
+
 language: cpp
-sudo: false
+
+matrix:
+  include:
+    - compiler: gcc
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+          packages:
+            - g++-4.9
+      env: COMPILER=g++-4.9
+    - compiler: gcc
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+          packages:
+            - g++-5
+      env: COMPILER=g++-5
+    - compiler: clang
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-precise-3.6
+          packages:
+            - clang-3.6
+      env: COMPILER=clang++-3.6
+    - compiler: clang
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-precise-3.7
+          packages:
+            - clang-3.7
+      env: COMPILER=clang++-3.7
 
 before_install:
+  - sudo apt-get update -qq
   - source <(curl -SLs https://raw.githubusercontent.com/fortyseveneffects/travis-ci-arduino/master/install.sh)
 
 script:
   - build_main_platforms
   - mkdir build && cd build
-  - cmake ..
+  - cmake -DCMAKE_CXX_COMPILER=$COMPILER ..
   - make
   - test/unit-tests/unit-tests