pytave: docs for building on Windows

[Colin Macdonald]

Abhinav,

Here are some notes I thought of, regarding documenting your efforts to 
get PyTave building on Windows:

1.  Please write this so that someone who has no idea what "mxe", 
"msys2", "mingw", "cygwin" are (*cough* me *cough*).

2.  However, you don't have to explain what everything is, just provide 
links and try to document as precisely as possibly what you tried. 
(e.g., what directories you install things into, what files you edited, 
etc).

3.  An "executive summary" of a few sentences of what the current blocks 
are (e.g., is it the boost dependency?)

4.  A summary of other approaches you tried that didn't work (and if you 
remember, what went wrong).

5.  Should we do this on the wiki?  That way, others (e.g., Tatsuro) can 
modify too.

6.  Incomplete is better than never, early-and-often, etc.

thanks,
Colin