Ignore case on WordsTable lookup

We wanna preserve case in the words returned, but the actual lookup should ignore case.

Why? It's a bit hard to express in words, but look at this case:

**Heard sentences**
- "Don't mind me"
- "I don't care"
- "I love you but I don't want to go to the supermarket"

When the generator hits "don't" and is looking for the next word, if we pay attention to case, it will use "care" or "want", but never "mind" since that was preceded by "Don't" rather than "don't".

Feels wrong to me. The case of the preceding word doesn't really matter for the current word to be picked. So let's ignore it.