remove dupe clang install

Author: Dane Springmeyer

.travis.yml

@@ -56,7 +56,6 @@ before_install:
  - |
    if [[ $(uname -s) == 'Linux' ]]; then
      export LDSHARED=$(python -c "import os;from distutils import sysconfig;print sysconfig.get_config_var('LDSHARED').replace('cc ','clang++-3.8 ')");
-     mason install clang 3.8.0
      ./.mason/mason install clang 3.8.0
      export PATH=$(./.mason/mason prefix clang 3.8.0)/bin:${PATH}
      which clang++