Spanish language fix (typos mostly, some usage)

Hi guys. Aidan said this was where the party was.

I thought I'd start contributing somewhere easy, so I've fixed some typos, a couple of inconsistencies (places where nothing was wrong, but I've unified two inconsistent usages), and some colloquial usage.

I haven't touched anything I didn't understand, anywhere that would have privileged one variant of Spanish over another, or where some discussion would be warranted. I'll come latter with a "to be discussed" pull request.