Version 0.2.1

• Stopped using traits for problem relations.
• Optimization models.
• Scalar expressions and variables.
• Functions: add, subtract, divide, multiply, negate, cosine, sine.
• Automatic differentiation.

Version 0.1.0

• Problem abstractions (Minlp, Milp, Nlp, Lp)
• Solver interfaces (Ipopt, Cbc, Clp)