v1.1.0

• Added memoize classes for efficient memoization of function calls.
• Improved lru_cache and added efficient multi-thread version using phmap comtainer and extended APIs.
• Added intrusive_ptr class modeled after the boost one.
• Suppress warning in btree.hpp
• Fix imperfect hash for tuple of small integers - better implementation of gtl::HashState().combine() from boost
• Switch to Semantic versioning scheme