Added Clang 5.0 tests

.travis.yml

@@ -27,11 +27,19 @@ matrix:
         apt:
           sources:
             - ubuntu-toolchain-r-test
-            - llvm-toolchain-precise-3.8
+            - llvm-toolchain-precise-3.6
           packages:
-            - clang-3.8
-      env: COMPILER=clang++-3.8
-
+            - clang-3.6
+      env: COMPILER=clang++-3.6
+    - compiler: clang
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-precise-5.0
+          packages:
+            - clang-5.0
+      env: COMPILER=clang++-5.0
 compiler:
   - clang