added hero sprites
move sprites file
add .gitignore
successful scaleable sprite map positioning test

Each hero sprite map places the character positions at the same pixel
locations. This means that actions can be set on a number of data
attributes and the correct character image will display.

All sizes are specified in `ems` off the base font-size of `10px`, so
that all game element scaling happens automatically when the font-size
is adjusted.

This hasn't tested animations, which may still pose a problem.