Cmake love (#55)

* Do CMake properly

* Remove uneeded file

* Add patch to version

* Init submodule in appveyor

* Use FetchContent

* Up CMake version requirement

* Use Xenial on Travis instead of Trusty

* Tidy traits

* Use Xenial repos

tests/emplace.cpp

@@ -1,5 +1,5 @@
 #include "catch.hpp"
-#include "expected.hpp"
+#include <tl/expected.hpp>
 #include <memory>
 #include <vector>
 #include <tuple>