Cleaned up Vector move assignment.

  template <class Container>

  ThisType& operator=(const Container& rhs);

  template <DeviceType device_name2, class Allocator2>

  ThisType& operator=(Vector<ScalarType, device_name2, Allocator2>&& rhs);

  template <class Allocator2>

  ThisType& operator=(Vector<ScalarType, device_name, Allocator2>&& rhs);

  // Returns the i-th element of the vector.

  // Preconditions: 0 <= i < size().first.

}

template <typename ScalarType, DeviceType device_name, class Allocator>

template <DeviceType device_name2, class Allocator2>

template <class Allocator2>

Vector<ScalarType, device_name, Allocator>& Vector<ScalarType, device_name, Allocator>::operator=(

    Vector<ScalarType, device_name2, Allocator2>&& rhs) {

    Vector<ScalarType, device_name, Allocator2>&& rhs) {

  static_cast<Allocator>(*this) = std::move(rhs);

  std::swap(data_, rhs.data_);

  std::swap(size_, rhs.size_);

  std::swap(capacity_, rhs.capacity_);