Update CI to test multiple python versions (#45)

* Update CI to test multiple python versions

* Ensure numpy is installed

* Handle lulesh with cmake < 3.16

* Fix typo

* Bump minimum CMake version to 3.16

- CMake 3.15 has issue with PTL object library

* Tweak CI test output

examples/user-api/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.16 FATAL_ERROR)
 
 project(omnitrace-user-api LANGUAGES CXX)