Caret fixes

[migueldeicaza]

Hello folks,

UIKit/AppKit improvements:

A long-standing limitation of SwiftTerm was that it did not render the caret with the specified color, and when it did, it was a solid block that would cover the underlying text. This is somewhat mitigated by the cleverly disguised hack that used a blinking cursor, as well as the support for bean and underline cursors.

The new version of SwiftTerm (1.2.1) will now use the configured caret color, and still render properly, as well as allowing you fine control over both the foreground and background colors (caretColor and caretTextColor properties) of the caret. If you do not set the caretTextColor, it will default to the foregroundColor configured on your view.