Vertical text cropping

If the label bounds are not high enough, CTFramesetterSuggestFrameSizeWithConstraints returns CGSizeZero and no text is rendered at all. By setting the text rect height to be twice the font point size, CTFramesetterSuggestFrameSizeWithConstraints doesn't return CGSizeZero thus the text is rendered cropped.
Add feature: custom truncation token string
Changing truncationTokenString to NSString, so that attributes are inherited correctly

Adding to documentation for truncationTokenString property
[Issue #154] Fixing touch event to cancel when touches move outside of bounds
Removing unnecessary -setLinkActive:withTextCheckingResult: method, in favor of simpler override of -setActiveLink:
Reset activeLink on setText: in case the update happens when a link is active
[Issue #150] Detecting links asynchronously in background queue
Removing unnecessary will/did change

nil-ing out dataDetector object if types is UIDataDetectorTypeNone
Removing unnecessary will did change methods
Merge pull request #159 from runmad/master

Set activeLink to nil on setText:
Adding more detail to inline comment about doubling point size
Merge branch '0xced-vertical-cropping'
Merge branch 'master' of github.com:mattt/TTTAttributedLabel
Bumping version to 1.5.0
Update README.md
Changing example in README to use ARC