CI: Update clang on travis

.travis.yml

@@ -1,13 +1,6 @@
 language: cpp
 sudo: false
 
-os:
-  - linux
-  - osx
-
-compiler:
-  - gcc
-  - clang
 
 # don't create redundant code coverage reports
 # - AUTOTOOLS=yes COVERAGE=yes BUILD=static
@@ -19,25 +12,40 @@ compiler:
 # this will still catch all coding errors!
 # - AUTOTOOLS=yes COVERAGE=no BUILD=static
 
-env:
-  - AUTOTOOLS=no COVERAGE=no BUILD=shared
-  - AUTOTOOLS=no COVERAGE=yes BUILD=static
-  - AUTOTOOLS=yes COVERAGE=no BUILD=shared
-
 # currenty there are various issues when
 # built with coverage, clang and autotools
 # - AUTOTOOLS=yes COVERAGE=yes BUILD=shared
 
 matrix:
-  exclude:
-    - compiler: clang
-      env: AUTOTOOLS=yes COVERAGE=yes BUILD=static
+  include :
     - os: linux
+      compiler: gcc
+      env: AUTOTOOLS=no COVERAGE=yes BUILD=static
+    - os: linux
+      compiler: gcc
+      env: AUTOTOOLS=yes COVERAGE=no BUILD=shared
+    - os: linux
+      compiler: clang++-3.7
+      env: AUTOTOOLS=no COVERAGE=yes BUILD=static
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-precise-3.7
+          packages:
+            - clang-3.7
+    - os: linux
+      compiler: clang
+      env: AUTOTOOLS=yes COVERAGE=no BUILD=shared
+    - os: osx
+      compiler: clang
       env: AUTOTOOLS=no COVERAGE=no BUILD=shared
     - os: osx
-      compiler: gcc
+      compiler: clang
+      env: AUTOTOOLS=no COVERAGE=yes BUILD=static
     - os: osx
-      env: AUTOTOOLS=no BUILD=static
+      compiler: clang
+      env: AUTOTOOLS=yes COVERAGE=no BUILD=shared
 
 script:
   - ./script/ci-build-libsass