List the plugin's external dependencies, currently only `mplayer` which
is used to play game audio.

To ensure that the help file opens at the top. Otherwise for some reason
it was opening at *space_vlaze-h* for me.

Otherwise the inputs get compared as strings and only the leftmost digit
of the number gets sorted so you end up with things like this:

    [8, 43, 2, 13, 0]

Convert our inputs to numbers so that they get compared in their
entirety and larger numbers move to the head of the list.

Didn't really like the last one so modified it a bit to try to make it
less harsh. Still not a huge fan but it's better than before.

List a few known bugs that currently appear in the game.

If the user has already defined a mapping for `<leader>sv` then don't
overwrite their mapping.

Also define a `<Plug>` mapping for this for users to map to if so
desired.

Originally thought of Maize but had misspelled it as Maze. Was
considering Maiz so as to not be so literal, then decided that a more
French spelling looked nicer.

Write Vim help for the plugin including an introduction, information
about the command and map provided, as well as gameplay instructions and
maps.

Also generate help tags.

Since we're handling game actions in `mappings#Listen()` now, don't call
our functions from these normal mappings.

The reason for not doing so is because otherwise after you get a Game
Over you could still move the player around and fire missiles (although
doing so wouldn't affect your score).

Set these keys to `<nop>` so that they don't do their normal Vim
functions so we can maximise the feeling of being in the game world
versus being in a text editor. Otherwise you can move your cursor
around, record macros with `q`, and I'm just not sure I want to allow
all that in the game.