Date parser: Should not ignore separators

[rxaviers]

Parsing a date with correct separator works and is correct:

> Globalize('en').parseDate('1/2/17', {skeleton: 'yMd'})
0017-01-02T02:00:00.000Z

Parsing a date with incorrect separator currently works, but it's correct:

> Globalize('en').parseDate('1-2-17', {skeleton: 'yMd'})
0017-01-02T02:00:00.000Z
> Globalize('en').parseDate('1.2.17', {skeleton: 'yMd'})
0017-01-02T02:00:00.000Z
> Globalize('en').parseDate('1.2.2017', {skeleton: 'yMd'})
2017-01-02T02:00:00.000Z
> Globalize('en').parseDate('10.2.2017', {skeleton: 'yMd'})
2017-10-02T03:00:00.000Z
> Globalize('en').parseDate('10a2a2017', {skeleton: 'yMd'})
2017-10-02T03:00:00.000Z