Release 3.1.0

Changes:

• Compounds may now be present more than once when constructing the kinetic model with the NetworkBuilder.
  The stoichiometries are then summed up accordingly.

Release 3.0.0

Changes:

• Update address in license
• Interface Sundials and add CVODE-BDF integrator

Release 2.0.0

Complete rewrite in C++ with the following features:

• Runge-Kutta type numerical integration of the differential equations
• Integration of vertex and edge fluxes
• Tracking of maximal concentrations
• Python bindings for all features