1.5.3.17 Rotating

• Rotates the order of the elements in the range [first,last), in such a way that the element pointed by middle becomes the new first element.
  for (int i=1; i<10; ++i) myvector.push_back(i); 
  // 1 2 3 4 5 6 7 8 9 
  rotate(myvector.begin(),myvector.begin()+3, 
                                               myvector.end()); 
                                // 4 5 6 7 8 9 1 2 3