--pledge and --additional-fixed fixes and invalid ascii characters fix

I have added ability to use --pledge with only 1 tier, as well, I fixed some --additional-fixed math logic and fixed a bug where script would abort if the kickstarter tier description has invalid ascii characters in it

 there is one bug in mine, which I could not figure out. I had to indent line 350 or else
 i get the following error
 line 367
   for stat, s, id, current_priority in zip(stats, selected, ids, priority):
TypeError: zip argument #1 must support iteration
 the line I had to intent was 350
if ids:

 i needed to add some tabs for me to get it to work, or else i get that error i just posted