Added first unit tests
Extra text for large images (like covers)

By adding these extra tests, I managed to find why the algorithm
sometimes added 1 line too many, so I was able to remove the
work-around of always having 1 blank line at the bottom.

This means more efficient usage of screen page when pagenumbers
are turned off.
Added pageturnning test.
Quick test for page turning.
Updated README to mention IntelliJ