Issue #26 Calculate slider factor based on width

The slider factor needs to account for the fact that the slider will never
reach the end of the track. Only expected the slider to reach its own width
proximity from the end of the track.
Issue #26 Keep image in frame during resize

While the image is being resized, keep it within the boundaries of the frame.
Issue #26 Detect if image is too small

If the image is too small to work with, do not allow it to be resized by scroll.