Bugfixes

This release addresses a number of minor bugs and provides some updated documentation, as well as gives a new definition for handling Lua compiled as C++.

Fixes:
#306 - Building Lua as C++ now has a definition to make it easier to work with sol2: http://sol2.readthedocs.io/en/latest/errors.html#linker-errors
#304 - LuaJIT condition fixes
#305 - default handlers becoming invalid for a given Lua state (still potentially problematic: e.g., see multiple Lua states and the fact that the function is static, provides a bit of a problem)
#301 - Thread state deadness was default-defined, now defined to an out-of-the-way value
#300 - Apple build failures not a problem, thankfully