Nitpicking sect6_joinongithub in index.en.json for consistency.
Translation to Nynorsk in index.no_NN.json
Renamed index.nb_NO.json to index.no_NB.json, fixed translation.

I renamed the file in order to comply with README.md. I also fixed translation some, it felt a little like Google Translate with various words feeling just slightly out of place from a native's point of view.
Delete index.nb_NO.json in favor of index.no_NB.json according to README.md
Rename index.no_NB.json to index.nb_NO.json
Rename index.no_NN.json to index.nn_NO.json
Merge pull request #81 from chinatsun/master

Translation to Norwegian Nynorsk. Nitpicking on the English original, and some further minor work done on Norwegian Bokmål.