Added SetTimeNow function to override global timeNow func

[cevaris]

Looking at logger.go, seems we default to Local time. Make sense for some, but it would be nice to be able to correlate logs with UTC time based events.

var (
    // Sequence number is incremented and utilized for all log records created.
    sequenceNo uint64

    // timeNow is a customizable for testing purposes.
    timeNow = time.Now
)

This PR adds and exposes a SetTimeNow(func() time.Time) function to provide the end user a choice whether to log using the default Local time, or UTC, or MST, etc.

func init() {
    backend1 := logging.NewLogBackend(os.Stderr, "", 0)
    backend1Leveled := logging.AddModuleLevel(backend1)

    // Log UTC time, default is Local
    logging.SetTimeNow(time.Now().UTC)

    logging.SetBackend(backend1Leveled)
}

[cevaris]

any thoughts @op ?

[smvv]

@op can you merge this PR? I would like to use the UTC timezone while formatting as well