Merge pull request #2 from indragiek/master

Accept NSString and NSURL for NSLinkAttributeName
Add tests for AppKit color conversion
Support justified text alignment
Update mn_initWithCoreTextAttributesFromHTMLString to work with subclasses.
AshtonHTMLReader +sharedInstance to +HTMLReader has the method returns no shared instance.
Merge pull request #4 from indragiek/master

Fix crashing bug when NSURL +URLWithString: returns nil
Replace string with constant
Fix bug where justified text alignment wasn't preserved
Merge remote-tracking branch 'origin/enhancements-MindNode'
Fix broken tests after rename sharedInstance -> HTMLReader
Convert windowBackgroundColor correctly and add test case for it
sharedInstance -> HTMLReader
Sanity check all AppKit inputs
Sanity check all UIKit inputs
Now this is embarrasing
Store a font's postScriptName and prefer the postScriptName when restoring
Explain why we ignore symbolic traits when a postScriptName is given