Update pypi version to use LuaJIT 2.0.4

[pablomayobre]

LuaJIT 2.0.4 was released recently, it would be nice to have the pypi binary updated to use this version, plus reflect the newest changes (though there arent that many)

Thank you for your work! Keep it up :+1:

[kmike]

lupa doesn't bundle luajit, is there anything to update in lupa to support 2.0.4?

[jneb]

There now are download instructions on using luajit in the readme. However, the pypi still gives the old version of lupa, which is 1.14. There are quite a few fixes since then.

[scoder]

Probably no longer an issue with Lupa 2.1.