Added lots of explanations/ease of use to the game:
Go Back by clicking/pressing esc
You can now go back in most menus by pressing esc or the right mouse button
Bugfixes to skill description
Some skills didn't have a description at the latest upgrade level
Difficulty Bonus Explanation
Added a note that says that the bonus xp and gold only applies after a run (not during a run)
Crypts Stage Explanation
Made it easier to understand this stage by adding arrows on the ground and more detailed text popups during the game play (e.g. kill the boss within the time limit)