-Make CEREAL_THREAD_SAFE be 0 or 1 instead of present or not present
-Move CEREAL_NOEXCEPT to macros.hpp
-instead of individual locks, can now use StaticObject::lock() to request a lock if CEREAL_THREAD_SAFE is enabled. If
not enabled, this call returns an empty object. The lock returned acts just like std::lock_guard, but uses
std::unique_lock internally
-Made a bunch of requests to StaticObject::getInstance const
-Added first stab at multithreaded tests with versioning and polymorphism
