[Wordlist] Easily add specific words to preloaded word lists

One may want to select a word list he likes, (e.g. rockyou.txt) and then happend to it (maybe at the beginning) specific words (e.g if I am cracking github's passwords I may want to add "Github" to my word list), creating thus a unique word list which would be used only for this run. 

The input of new words should be quick and easy to do for the user.