Added OSX build on Travis

scripts/travis/cmake.sh

@@ -1,6 +1,8 @@
 #!/bin/sh -eux
 
-curl -sS https://cmake.org/files/v3.4/cmake-3.4.0-Linux-x86_64.tar.gz | tar xz -C /tmp --strip 1
+URL=https://cmake.org/files/v3.4/cmake-3.4.3-Linux-x86_64.tar.gz
+
+curl -sS $URL | tar xz -C /tmp --strip 1
 
 /tmp/bin/cmake -DCMAKE_CXX_COMPILER=$CMAKE_CXX_COMPILER .
 make