Rikaikyun v0.15 Beta

Fixed some scrolling issues and added basic navigation.

Known issues:

• you can navigate an empty document
• scrolling to 100% using navigation might lead to some unpredictable results (position tracking is based on upper edge, meaning you never reach 100%, but only 100% - 1 page worth of text)
• When your position is past 100% - 1 page, you can only scroll the text by touching the text and not the whole screen