Add some ignoreCase methods, rename stringCI to ignoreCase

[johnynek]

follow up to #46

What do you think @stephenjudkins ? I want to publish a new version, but the name just wasn't sitting well with me.

Can you review this and the other new methods I added?

There is one ambiguity: string can be converted to Iterable[Char] in scala, so I added ignoreCaseChar and ignoreCaseCharIn but to save space for the common case, I used ignoreCase to accept a string. A clearer, but more verbose approach would be to do ignoreCaseString, but I feel that's a bit long. That said, ignoring case isn't that common, so maybe that's okay. I don't know.

[stephenjudkins]

👍 i think this all looks great. I picked stringCI simply because it was the name use in atto but I like these a bit better. I wouldn't quibble too much about ignoreCaseString vs ignoreCase, I think having string be the "default" thing is probably what 99% of parsers will be doing