Make all mappings nonrecursive

As Steve Losh put it in Learn Vimscript the Hard Way:

> When should you use these nonrecursive variants instead of their
> normal counterparts?
>
> Always.
>
> No, seriously, *always*.

I'm also updating the whitespace used for the mappings to allow for
future mappings to be easier to read. The spacing was picked to allow
for the use of `<silent>` and `<leader>` without things getting too
cramped.