Boris Sozin

Looks like slack refuses to accept milliseconds in [ formatting](https://api.slack.com/reference/surfaces/formatting#date-formatting). Example of [acceptable message](https://app.slack.com/block-kit-builder/T08QRUZ6W#%7B%22blocks%22:%5B%7B%22type%22:%22section%22,%22text%22:%7B%22type%22:%22mrkdwn%22,%22text%22:%22%3C!date%5E1392734382%5EPosted%20%7Bdate_num%7D%20%7Btime_secs%7D%7CPosted%202014-02-18%206:39:42%20AM%20PST%3E%22%7D%7D%5D%7D). And example of [unacceptable one](https://app.slack.com/block-kit-builder/T08QRUZ6W#%7B%22blocks%22:%5B%7B%22type%22:%22section%22,%22text%22:%7B%22type%22:%22mrkdwn%22,%22text%22:%22%3C!date%5E1392734382.000000%5EPosted%20%7Bdate_num%7D%20%7Btime_secs%7D%7CPosted%202014-02-18%206:39:42%20AM%20PST%3E%22%7D%7D%5D%7D). Therefore [Extensions.ToProperTimeStamp](https://github.com/Inumedia/SlackAPI/blob/1c51217e0e0ad3aab692d0d8722b9aa21b9c24a8/SlackAPI/Extensions.cs#L21) which always produce 6 decimal digits generates timestamp not...

Origin header for CORS

1

Trying to play with rest api using RESTED in firefox. Server tells me `403 Forbidden: Responding with 403 status code due to failed CSRF check: request's "Origin" header value "moz-extension://306828c6-2667-4649-a88d-296116e4bda7"...