Added support to Swift 5

The 0.4.x versions will have support for Swift 5.

If you want to use the Swift 4 version, please refer to a 0.3.x version.

Added Swift 4 support

This version adds support to Swift 4.

The interface of the two convenience methods to add attributes to substrings was changed:

func set(attribute: String, value: AnyObject, onSubstring substring: String)
func set(attribute: String, value: AnyObject, onRange range: NSRange)

was updated to

func set(attribute: NSAttributedStringKey, value: Any, onSubstring substring: String)
func set(attribute: NSAttributedStringKey, value: Any, onRange range: NSRange)

Since we now have a new type NSAttributedStringKey that was introduced in Swift 4, we are leveraging it when adding attributes to substrings.

Added proper documentation and examples

Usage examples were added on the "Example" project.

This version requires the following to run:

• iOS 9 or greater;
• Swift 3;
• Xcode 8

Fixed core files not being imported

All the main files were not being properly used when consuming the library using cocoapods since they were not on the correct folder. This version fixes that issue.
Also, added a small example in the Example Project using the library.

First Beta Release

This version should be fully functional with support for Swift 3.