Mojo for Python extensions

[prabhuramachandran]

Thank you for Mojo, this is an exciting development!

Given that Mojo is currently a work in progress, I was thinking that it might make sense to allow folks to use Mojo to create Python extensions. This way Python programmers could slowly migrate to using Mojo instead of Cython/C/C++ or whatever else to write their extension modules and benefit from the very nice features of Mojo without requiring that Mojo be feature complete. I can see that Mojo would be immediately useful to many even as it currently stands given the really powerful building blocks that it provides.

p.s. I did notice that there is a mention of this in #117 but my point here is to not necessarily wait until Mojo is at 1.0 for something like this.