Add support for the "date-time" type

[n1k0]

JSONSchema defines a date-time type which doesn't seem to be supported atm by the library (while date oddly does):

> require("jsonschema").validate("aaa", {type: "date-time"})
ValidatorResult {
  instance: 'aaa',
  schema: { type: 'date-time' },
  propertyPath: 'instance',
  errors: [],
  throwError: undefined,
  disableFormat: false }

I'm using jsonschema v1.0.2.

Also it appears that unknown types from the lib will always pass validation, which sounds a little dangerous if you ask me -- though that's probably another issue.

Could we consider bringing support for date-time validation?

[n1k0]

Oh my bad, I've misread the spec, and date-time is a format and not a type! Closing, sorry for the noise.