Completed() method should call t.Complete() before .Bool()

[0abdelilah]

Hi! I noticed in Torrent.Completed():

func (t *Torrent) Completed() bool {
    return t.Complete.Bool() // Error
}

t.Complete is actually a function returning ReadOnlyFlag, so the correct code should be:

func (t *Torrent) Completed() bool {
    return t.Complete().Bool() 
}

This avoids the "undefined" compiler error.

[aliworkshop]

@0abdelilah thanks for reporting.
please create new PR + unit test about this change.