DateTimeService unable to parse date 01-01-1970 in UTC

Description:
In the DateField component if I introduce the date 01-01-1970 with the keyboard I've got a 'Date format not recognized' error and
in the console I've got "java.lang.IllegalArgumentException: Parsing of '01-01-1970' failed".
This only happens if I have the Windows in UTC time.

I take a look in the code and find why this is happens, in the class com.vaadin.client.DateTimeService method parseDate (line 485) you have this if:

// Some version of Firefox sets the timestamp to 0 if parsing fails.
if (date != null && date.getTime() == 0) {
	throw new IllegalArgumentException(
			"Parsing of '" + dateString + "' failed");
 }

the date 01-01-1970 in UTC it's zero, so it always throw the exception.

For example

SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
Date d = sdf.parse("01-01-1970");
System.out.println(d.getTime());		// prints 0
System.out.println(new Date(0).getTime()); 	// prints 0

Tested with:
Vaadin 8.0.3
Windows 7
Chrome 56
Windows Timezone: (UTC+00:00) Dublin, Edimburgo, Lisboa, Londres
Windows Regional Settings: Portugal dd-MM-yyyy

Start in com.vaadin.client.DateTimeService.parseDate around line 485 and reproduce the DateField input with UTC timezone and the 01-01-1970 value. Check the existing parsing-failure handling and add coverage for this epoch date; done means valid UTC input is accepted while genuinely failed parsing still reports an error.