accept moment.js instances for project startDate/endDate

I wanted to have my projects use moment.js instances for start/end dates so that I could easily handle intra-day timestamps (upcoming pull request).

`isNaN` checks [are problematic](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/isNaN#Description), and returns the wrong result for moment.js:

	foo = moment()
	isNaN foo
	# => false

Switching the `project` setup code in `parseData` to use `typeof` fixes the problem.

*Note:* I didn’t change the `task.date` check in `parseData` since I’m not using tasks—but I imagine it has the same problem. Also, I didn’t change the minified version.