Finished an icelandic translation of the app

I finished an Icelandic translation of the app. After finishing the translation, I used the app a few times and asked a few friends to try it out as well. I then changed small inaccuracies or instances where the language was not clear.

I used the Icelandic translation for Git (can be found here: https://gist.github.com/avar/425917) as a foundation which I built upon.