Fix for issue #1873
Fix for issue #1873

Attempt parsing object (ex Moment.js date object) to date. This was implicitly supported <= 0.4.10 but regressed with narrower validation in #1121.

alanhamlett/c3,masayuki0812/c3,aendrew/c3,naver/billboard.js,alanhamlett/c3,masayuki0812/c3,c3js/c3,c3js/c3,naver/billboard.js,c3js/c3,naver/billboard.js,naver/billboard.js,aendrew/c3,c3js/c3,alanhamlett/c3,Aloomaio/c3,Aloomaio/c3