letting native date construct date

[swilliamset]

instead of moment falling back to native date
bypasses deprecated warning
fix #915

[futuremint]

I'm not entirely sure just sending the string through new Date here is a good idea. Newing up Date objects can throw exceptions if the string if not formatted correctly, which is handled down lower on line 371. This should probably either be safer, or this entire chunk of code re-written to consolidate some of the error handling code pieces.

[interactivellama]

Bookmarking this moment.js issue before I merge: Be careful when falling back to Date constructor

tl;dr version:
Dev's just want date parsing to magically happen, but moment only take ISO now unless you provide a format. Use of native browser Date() has been removed for parsing due to differences between browsers. Now moment fires an error if it's not getting ISO format. Although as you can see, we are using Date() to parse before we pass to moment unless a format is provided.