Updating linkPurpose.linksMoreThan4Chars to be linkPurpose.linksAtLeast4Chars, to match the rule as stated in http://www.openajax.org/member/wiki/Accessibility_-_WCAG20_Validation_Rules.  Including Rule URL in the definition.  Updating message text to be "4 or more" characters versus "more than 4"
Merge pull request #16 from DuaneOBrien/master

Fixes linkPurpose.linkHasMoreThan4Chars issue