Update date input handling to match valueAsDate

input.value = '2013-04-27'
input.valueAsDate.toGMTString() = 'Sat, 27 Apr 2013 00:00:00 GMT'
[current autoform date parsing logic].toGMTString() = 'Sat, 27 Apr 2013 07:00:00 GMT'
Update dateToFieldDateString output to UTC to match handle date input & HTML 5 spec
Merge pull request #30 from mjgallag/patch-1

Update date input handling to match valueAsDate