Fixing Mouse

Mouse changes:
+ `Mouse.click?` now returns `true` upon release if the mouse hasn't moved since triggering. `Mouse.press?` didn't change.
+ `Mouse.dragging?` now returns `true` only if the mouse has moved since triggering (and is still pressing `mouse_left`).
+ `Mouse.rect` now returns `false` when not dragging.
+ `Mouse.last_rect` is now `false` by default.
+ `Mouse.last_rect` now becomes `false` when the mouse clicks.

Other changes:
+ Some typos and stuff