Remove extra data from Stack Exchange sites (including Stack Overflow)

[mathvav]

Handle cleaning stuff from Stack Overflow links.

Acceptance criteria:

• Changes links like https://stackoverflow.com/questions/18537257/how-to-get-the-directory-of-the-currently-running-file into https://stackoverflow.com/questions/18537257
• Keeps the #comment on links such as https://stackoverflow.com/questions/18537257/how-to-get-the-directory-of-the-currently-running-file#comment77516477_18537257
• Changes links like https://stackoverflow.com/questions/18537257/how-to-get-the-directory-of-the-currently-running-file/18537792#18537792 or https://stackoverflow.com/questions/18537257/how-to-get-the-directory-of-the-currently-running-file#18537792 into https://stackoverflow.com/questions/18537257#18537792 (this scrolls to a specific answer)
• Works for Stack Overflow
• Works for other Stack Exchange sites (perhaps there is an online list of all the domains?)
• Sufficient unit tests are added