Install python 2 and 3 in the "wrong" order

[Nagy László Zsolt]

> 	I should emphasize that this is with the /same/ x.y version...
> Installing 3.3 when the previous was 3.2 won't overlay.
>
> 	Though I don't see anything in the ActiveState builds (which are all
> I've ever used) to handle the #! type selection of the desired version.
> Just got done updating my 2.7, replacing 3.2 with 3.3, and then having to
> edit my path to make 2.7 primary... No "py.exe"
I need both 2.7 and 3.3. And apparently, py.exe does not work the way it 
should be.

I would happily reinstall 3.3 to solve the problem, but before I do that 
I would like to check all other related settings. So that after I 
reinstall 3.3, I will exactly know what was happening.

It might be a good idea to change the installer of the 2.x series to 
detect if 3.x is already installed, and handle assignments of py and pyw 
files gracefully.