TODO
=== Suggestion from JSS paper ===
* Fix warnings in dtwWindow.plot DONE
* Add dtw.print method DONE
* Make type="l" default for dtw.plot DONE
* Use NAMESPACE feature DONE
=== Other ===
* Optimize memory use (e.g. pass distance.only to the native
implementation and avoid returning the two large matrices)
TEST CASE for Itakura
1 0 1 1
1 1 10 10
1 1 10 10
Type IV: 3 ?
Itakura: 13 ?