Updated credits and changes.txt.
Minor change to var name for clarity.
Made the top atoms be translated by the model instead of in the AtomCanvas so that their evaporation trajectory isn't related to the top book's motion, see #21.
Optimization of top book translation motion, see #21.
Increased size of reset buttons, see #20.
Updated changes.txt.
Fixed an issue where the bottom of the thermometer appeared cut off in Firefox on Mac, see #18.
Merged in changes from the master branch, which include fixes for several bugs reported on the release candidate.