Typo in expectation, extend really does copy undefined properties

Based on https://github.com/jashkenas/underscore/issues/123, it appears this assertion was inverted but the language was never updated to reflect it.
Rewording extend assertion
Merge pull request #1259 from hackreactor/master

Typo in expectation, extend really does copy undefined properties
Improved licenses part of package.json
Merge pull request #1263 from zubairov/patch-1

Improved licenses part of package.json