Fix and improve texts

[maxanier]

Split from issue #122, created by @EpicCreeperHD:

The book and other text-based things in the mod are poorly written. There's a few grammar mistakes here and there, which is fine for the most part as we can easily fix it (we have a rewritten version with some better grammar and more detailed information), but the descriptions for some things are often quite vague. Like the realistic mode for example. We have no idea what it changes.

[MarioSMB]

Another text to note is the "You can only sleep at day" message; "You can only sleep during the day" would be a grammatically correct statement.