userdata member variables are now supported
userdata now performs lookup based on tables
userdata now has reduced number of vector tables
userdata garbage collection improved
debug.hpp - new header for debugging problems with stack, mostly for internal use
Updated examples and readme changes to reflect new API (userdata example kept erroneous info that `userdata<T>` must be kept alive)
Some missing support for reference-style (l-value reference and pointer) calls from lua. Fixed.
Add include for std::free from <cstdlib>
Update bootstrap.py to handle external lua directories and linking on
linux.
Add uninstall and install targets to ninja.