Changed version to be appropriate for master branch, cleaned up changes.txt.
Made fluid and gravity revert to default values when the other is selected as the mystery quantity in the mystery pool, fixes #50.
Improved the fix for resetting default values to fluid and gravity when the other is chosen as the mystery quantity for the mystery pool, see #50.
Moved the textual readout so that it doesn't obscure the max and min positions of the needle, fixes #52.
Added more range to the fluid densities, fixes #51.
Merged in some fixes from the master branch.