release/0.0.2

New features:

• support for custom allocators
• index-based access to underlying array
• owner-based ordering using owner_before method and owner_less function object
• make weak_rc_ptr::lock() method return default initialized rc_ptr when expired() == true
• make_rc function

Bug fixes:

• fixed double-free problem when using enable_rc_from_this

release/0.0.1

Basic implementations of rc_ptr, weak_rc_ptr and enable_rc_from_this.