Merge pull request #1300 from gennadiycivil/master

Workaround for Travis issue https://goo.gl/d5eV8o

.travis.yml

@@ -9,7 +9,7 @@ install:
 # /usr/bin/clang is 3.4, lets override with modern one.
 - if [ "$CXX" = "clang++" ] && [ "$TRAVIS_OS_NAME" = "linux" ]; then export CXX="clang++-3.7" CC="clang-3.7"; ln -sf /usr/bin/ccache /$HOME/bin/$CXX; ln -sf /usr/bin/ccache /$HOME/bin/$CC; fi
 # ccache on OS X needs installation first
-- if [ "$TRAVIS_OS_NAME" = "osx" ]; then brew install ccache; export PATH="/usr/local/opt/ccache/libexec:$PATH"; fi
+- if [ "$TRAVIS_OS_NAME" = "osx" ]; then brew update; brew install ccache; export PATH="/usr/local/opt/ccache/libexec:$PATH"; fi
 # reset ccache statistics
 - ccache --zero-stats
 - echo ${PATH}