Fix directive starting with null Date. Improve ISO parsing.

Geomoment directive was broken for null dates.

Parsing of strings was relying on moment's mysterious internal parsing
which throws deprecated warnings when it has to pass through to to Date.
Moment supports ISO 8601, so do a simple regexp to reasonably guess
about that.
Fixed output format specifier lookup for Date/moment

- Also updated the test data time to be explicitly in UTC time.
Merge pull request #8 from goodeggs/iso-dates

Fix directive starting with null Date. Improve ISO parsing.