change link of chapter_basic

Author: emgeee

a-better-way-to-learn-swift.mdown

@@ -3,14 +3,14 @@
 
 [chapter_tour]: https://developer.apple.com/library/prerelease/mac/documentation/Swift/Conceptual/Swift_Programming_Language/GuidedTour.html#//apple_ref/doc/uid/TP40014097-CH2-XID_1
 [chapter_basics]: https://developer.apple.com/library/prerelease/mac/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html
+[optionals_basics]: https://developer.apple.com/library/prerelease/mac/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html#//apple_ref/doc/uid/TP40014097-CH5-XID_485
 [chapter_extensions]: https://developer.apple.com/library/prerelease/mac/documentation/Swift/Conceptual/Swift_Programming_Language/Extensions.html#//apple_ref/doc/uid/TP40014097-CH24-XID_229
 [solutions]: http://blog.swiftcast.tv/the-swift-programming-language-solutions-to-experiments/
 [swift_js]: http://realm.io/news/swift-for-javascript-developers/
 [operators]: http://nshipster.com/swift-operators/
 [reserved_words]: http://blog.swiftcast.tv/articles/reserved-words-escaping
 [values_vs_reference]: https://developer.apple.com/swift/blog/?id=10
 [compound_vs_named]: https://developer.apple.com/library/prerelease/mac/documentation/Swift/Conceptual/Swift_Programming_Language/Types.html
-[chapter_basics]: https://developer.apple.com/swift/blog/?id=12
 [optionals_case]: https://developer.apple.com/swift/blog/?id=12
 [swift_defines_away]: https://medium.com/@rrridges/swift-optionals-a10dcfd8aab5
 [chapter_functions]: https://developer.apple.com/library/prerelease/mac/documentation/Swift/Conceptual/Swift_Programming_Language/Functions.html
@@ -231,7 +231,7 @@ and increase the type safety of your code.
 
 #### Readings
 
-* [x]: Read the section called "Optionals" in "The Basics Chapter" of the Swift ebook.
+* [x]: Read the [section called "Optionals"][optionals_basics] in "The Basics Chapter" of the Swift ebook.
 * [x]: Read ["How Swift "Defines Away" Common Programming Errors…sort of"][swift_defines_away] by Matt Bridges
 * [x]: Read ["Optional Case Study: Value for Keys"][optionals_case] from the Swift Blog