Rewrite bootstrap script for clarity

Hello,

I rewrote the install script for some mysterious reason. As short and uninteresting as it was, I suppose something irked me about it and I rewrote it. The changes are all cosmetic, except for the `stream.isatty()` check, which hardly matters. 

Feel free to ignore this :)

Regards,
Georgi
Why?  What's the point in adding a local variable that's only used once for a function argument?!