Fix macOS build on Swift 3.2.

Fixes SpellingState attribute for macOS on Swift 3.2. See #15 for more details.

Support for watchOS, macOS, and tvOS

• Multiplatform support (iOS, macOS, watchOS, tvOS)
• Additional macOS-specific attributes
• Added VerticalGlyphForm enum and attribute
• Methods to convert between attribute dictionaries and Attribute arrays (#6)
• Methods to enumerate attributes
• Example app for macOS
• Lots of tests

Version 3.0.0

This release provides a more fully-featured, Swifty API for most uses cases of attributed strings on iOS. Updates include:

• A new Attribute enum that serves as a replacement for the key-value pairs of Foundation's API for attributed strings
• New extensions for adding, modifying, and reading attributes using the new Attribute enum
• More "Swifty" alternative methods for NSAttributedString and NSMutableAttributedString
• Support for iOS 8
• And more... !

2.0: Swift 3 Compatibility and API Improvements

• Added compatibility with Swift 3
• Introduced two new enums for API clarity
• Minor improvements to API
• Fully tested

1.0

Initial release.