Validates a string to have valid date format
npm install chai-date-stringUsage example:
`` javascript
var chai = require('chai')
, expect = chai.expect
, chaiDateString = require('chai-date-string');
expect('2015-11-12').to.be.a.dateString(); // will pass
expect('2015-24-12').to.be.a.dateString(); // will fail
`
It will validate time part as well.
The later will fail with message: AssertionError: expected '2015-24-12' to be a date string.