Issue with BytesQueue.

I was going through the `bytes_queue.go` and have found some inconsistencies with the result. Below is a way to reproduce this issue :

There is test in `bytes_queue_test.go` :

```go
func TestUnchangedEntriesIndexesAfterAdditionalMemoryAllocationWhereTailIsBeforeHead(t *testing.T) {
t.Parallel()

// given
queue := NewBytesQueue(100, 0, false)

// when
queue.Push(blob('a', 70)) // header + entry + left margin = 72 bytes
index, _ := queue.Push(blob('b', 10)) // 72 + 10 + 1 = 83 bytes
queue.Pop() // space freed at the beginning
queue.Push(blob('c', 30)) // 31 bytes used at the beginning, tail pointer is before head pointer
newestIndex, _ := queue.Push(blob('d', 40)) // 41 bytes needed but no available in one segment, allocate new memory

// then
assertEqual(t, 200, queue.Capacity())
assertEqual(t, blob('b', 10), get(queue, index))
assertEqual(t, blob('d', 40), get(queue, newestIndex))
}
```

Now lets change this test and bit and add the following line :

```go
func TestUnchangedEntriesIndexesAfterAdditionalMemoryAllocationWhereTailIsBeforeHead(t *testing.T) {
t.Parallel()

// given
queue := NewBytesQueue(100, 0, false)

// when
queue.Push(blob('a', 70)) // header + entry + left margin = 72 bytes
index, _ := queue.Push(blob('b', 10)) // 72 + 10 + 1 = 83 bytes
queue.Pop() // space freed at the beginning
queue.Push(blob('c', 30)) // 31 bytes used at the beginning, tail pointer is before head pointer
newestIndex, _ := queue.Push(blob('d', 40)) // 41 bytes needed but no available in one segment, allocate new memory

// then
assertEqual(t, string(blob('b', 10)), string(pop(queue))) // THIS LINE ADDED
assertEqual(t, 200, queue.Capacity())
assertEqual(t, blob('b', 10), get(queue, index))
assertEqual(t, blob('d', 40), get(queue, newestIndex))
}
```


As seen in the above screen shot, the expected string should be `blob('b',10)` and not `blob('c', 30)`.

I have pointed the bug happening in the `allocateAdditionalMemory` :

```go
if leftMarginIndex != q.rightMargin {
copy(q.array, oldArray[:q.rightMargin])

if q.tail <= q.head {
if q.tail != q.head {
headerEntrySize := getUvarintSize(uint32(q.head - q.tail))
emptyBlobLen := q.head - q.tail - headerEntrySize
q.push(make([]byte, emptyBlobLen), emptyBlobLen)
}

q.head = leftMarginIndex // Why are we doing this ?
q.tail = q.rightMargin
}
}
```

Ideally we should not be assigning `q.head = leftMarginIndex` this way you are actually breaking FIFO rules.