Seperator typo - should be separator

[DimitarVanguelov]

Hi, I'm new to GitHub and Julia (and programming in general), so apologies if this isn't the correct avenue for this type of "contribution" . I noticed that one of the variables in the digitsep function, called seperator is a misspelling of the word "separator". Not a biggie obviously, but thought I'd point it out. (Lovely package btw -- I think I learned a lot just by looking through it.)

Edit: created a pull request for this fix after I figured out how to do a pull request.