The body of a for in should be wrapped in an if statement to filter unwanted properties from the prototype

JSLint Documentation: http://www.jslint.com/lint.html#forin
StackOverflow Discussion: http://stackoverflow.com/questions/1963102/what-does-the-jslint-error-body-of-a-for-in-should-be-wrapped-in-an-if-statemen
Fixed typo
Fixed: Missing 'new' prefix when invoking a constructor
Merge pull request #19 from sqren/master

More JSHint fixes