Updates doctest and fixes issues with g++4.7 and MSVC2013 doctest
builds.
Adds new CI targets for g++ 9 and 10, clang 9 through 12.
Adds CI badges for github actions.
use docker containers
remove sudo
install software-properties-common
update before trying install
install wget
cmake and make
install cmake from pip
add apt-transport-https
Use llvm xenial
Fix clang package name
Fix boost with gcc<5
verbose compile
skip boost for gcc<5
macos test
skip boost for macos
test different xcode compilers
use new cmake syntax for selecting platform
no xcode 10 installed
Rename tests
