List of changes from version 2.21:

- Added dual license (GPL + UCLB)
- Updated block.h.

List of changes from version 2.1:

- Put the code under GPL license

List of changes from version 2.02:

- Fixed a bug in the implementation that uses forward star representation

List of changes from version 2.01:

- Added new interface function - Graph::add_tweights(Node_id, captype, captype)
  (necessary for the "ENERGY" software package)

