Fixed Issue #1357 - viB selects too much

This is my first contribution to any F# project and to VsVim so if you have any feedback about the contribution please let me know and I'll try to sort it out.

Thanks for a great plugin!
Similar comment here about line endings.  Unfortunately there isn't a handy property to use here.  This is the code I would use instead 

    let line = SnapshotUtil.GetLineOrFirst span.Snapshot (span.End.GetContainingLine().LineNumber - 1)
    line.End