add g++-6 to ubuntu-14.04 (#1144)
add g++-6 to ubuntu-14.04 (#1144)

* add g++-6 to ubuntu-14.04

* fix syntax

* fix yamllint errors for build-and-test

* fix 'add-apt-repository' command not found

* make 'run tests' explicit

* enable testing and run both release and debug

* oops
mockingbirdnest/benchmark,mockingbirdnest/benchmark,google/benchmark,google/benchmark,mockingbirdnest/benchmark,google/benchmark,mockingbirdnest/benchmark