Update books

## reference

3 commits in fa5dfb8..320d232
2019-09-16 20:42:56 +0200 to 2019-10-01 17:05:35 +0200
- Update async/await keywords to real keywords. (rust-lang/reference#687)
- Remove the warning that appears on every page. (rust-lang/reference#685)
- Eschew fp lit pattern (rust-lang/reference#683)

## book

9 commits in 871416b85c1a73717d65d6f4a9ea29e5aef3db0e..04806c80be0f54b1290287e3f85e84bdfc0b6ec7
2019-09-16 09:46:20 -0400 to 2019-10-01 20:20:22 -0400
- Fix tidy error. (rust-lang/book#2104)
- Fancy quotes
- Commit autogenerated cargo content
- Move all scripts into tools
- We can start lines with numbers without creating ordered lists
- ci: validate that all used references are defined (rust-lang/book#2032)
- Remove the check for unstable features
- Specify the rustc version we're using in a rust-toolchain file
- Fix broken link to Chapter 13-01 in Chapter 12-04 (rust-lang/book#2025)

## rust-by-example

9 commits in 67cfbf31df880728dcf7cb35b15b028ec92caf31..a6288e7407a6c4c19ea29de6d43f40c803883f21
2019-09-18 09:36:40 -0300 to 2019-10-01 10:09:14 -0300
- Add reference to lifetime in structs (rust-lang/rust-by-example#1274)
- Rectangle ambiguity (rust-lang/rust-by-example#1270)
- Make Parsing a String code editable (rust-lang/rust-by-example#1268)
- Fix match range pattern usage (rust-lang/rust-by-example#1269)
- Added type alias enum variant rfc (rust-lang/rust-by-example#1267)
- Chapter 9.2.5: impl FnOnce() works in 1.35 (rust-lang/rust-by-example#1266)
- Move chapters from folder "traits" to "trait" (rust-lang/rust-by-example#1263)
- Capturing changes (rust-lang/rust-by-example#1265)
- Fix rust-lang/rust-by-example#1261: document Iterator::position (rust-lang/rust-by-example#1262)

r? @ghost