Reduce cost of including chaiscript.hpp

- ChaiScript no longer includes or automatically instantiates std lib
 - ChaiScript constructor now requires an std lib instance in the form
   of a ModulePtr object
 - This new layout facilitates better usage of compilation firewalls and
   factories for reducing the overall impact of ChaiScript on a project

unittests/multifile_test_chai.cpp

@@ -1,7 +1,9 @@
 #include "multifile_test_chai.hpp"
 
+#include <chaiscript/chaiscript_stdlib.hpp>
+
 Multi_Test_Chai::Multi_Test_Chai()
-  : m_chai(new chaiscript::ChaiScript())
+  : m_chai(new chaiscript::ChaiScript(chaiscript::Std_Lib::library()))
 {
 }