Correct the README and other in-app text

I've rewritten the README changing the style from title case to standard case and corrected messages in the program itself. Some people, especially not so tech-savvy ones, might find the strange style of the README to be quite suspicious, thus making them believe this tool is not legit. I also have renamed `ico.ico` to `icon.ico` and removed the unnecessary `else` clause since it is not really possible for the program to get to it under any circumstances.