First update to the RxSwift book with version 1.1

This is a short update about the first update to our RxSwift book. First of all, we’d like to thank all of you who posted to our book errata forum! (and if you haven’t hit the forums yet, check ‘em out - it’s the best place to report typos, bugs, and more: ). I’ve worked with the team on a number of books and I must say the RxSwift book has had, so far, the most enthusiastic feedback - we’ve been drowned in questions, thank you messages, and typo/bugs reports.