Remove clang for now

It appears that the `libc++` available on Ubuntu 14.04 is broken and
doesn't handle the boolean regex correctly. Newer versions appear to be
correct but I have to work out how to get 14.04 to use it.

.travis.yml

@@ -21,22 +21,22 @@ matrix:
           packages:
             - g++-5
           sources: *sources
-    - os: linux
-      env: COMPILER=clang++-3.8 CXXFLAGS=-stdlib=libc++
-      addons:
-        apt:
-          packages:
-            - clang-3.8
-            - libc++-dev
-          sources: *sources
-    - os: linux
-      env: COMPILER=clang++-3.8 CXXFLAGS=-stdlib=libc++ UNICODE_OPTIONS=-DCXXOPTS_USE_UNICODE_HELP=Yes
-      addons:
-        apt:
-          packages:
-            - clang-3.8
-            - libc++-dev
-          sources: *sources
+#    - os: linux
+#      env: COMPILER=clang++-3.8 CXXFLAGS=-stdlib=libc++
+#      addons:
+#        apt:
+#          packages:
+#            - clang-3.8
+#            - libc++-dev
+#          sources: *sources
+#    - os: linux
+#      env: COMPILER=clang++-3.8 CXXFLAGS=-stdlib=libc++ UNICODE_OPTIONS=-DCXXOPTS_USE_UNICODE_HELP=Yes
+#      addons:
+#        apt:
+#          packages:
+#            - clang-3.8
+#            - libc++-dev
+#          sources: *sources
 script: >
     cmake -DCXXOPTS_BUILD_TESTS=ON -DCMAKE_CXX_COMPILER=$COMPILER
     -DCMAKE_CXX_FLAGS=$CXXFLAGS $UNICODE_OPTIONS .