README incorrectly defines msecs

[rmm5t]

The README docs for the v1() options states:

msecs - (Number | Date) Time in milliseconds since unix Epoch. Default: The current time is used.

But Date instances do not work as expected. Only millisecond values do:

> uuid.v1({ msecs: new Date() })
'00000000-0000-1000-b5d5-0d7fa4a8285e'

> uuid.v1({ msecs: new Date().getTime() })
'3a7ea410-effa-11e7-b5d5-0d7fa4a8285e'

I'm happy to submit a PR to fix this, but is this something where you would like the README to be corrected, or would you like the v1() implementation to accept Date instances for the msecs option?