Clang 5.0 CI build temporarily disabled as it's installation is broken

on Travis CI (workaround for #72).

.travis.yml

@@ -28,13 +28,13 @@ matrix:
           packages:
             - g++-5
           sources: *sources
-    - env: CXX=clang++-5.0 CC=clang-5.0
-      addons:
-        apt:
-          packages:
-            - clang-5.0
-            - libc++-dev
-          sources: *sources
+    #- env: CXX=clang++-5.0 CC=clang-5.0
+      #addons:
+        #apt:
+          #packages:
+            #- clang-5.0
+            #- libc++-dev
+          #sources: *sources
     - env: CXX=clang++-4.0 CC=clang-4.0
       addons:
         apt: