Move spectime into spectime-core subdirectory

Ready for creating a spectime-test
assertDateEquals() - better error message than assertEquals(Date, Date)

Includes milliseconds in the error message.
Create date/time with millis: date("2013-12-31 13:59:59.123")
date("2013-12-24 13:59") and date("2013-12-24 13:59:59")
tweak README for spectime-test