2-stage updates

v0.5.0

Fix name

L2 Loss and minimum bound

v0.4.0

Update REQUIRE

Add the `prob_generator` interface

v0.3.0

allow prob_generator

Two-stage method, Monte Carlo support, parameter interface

v0.2.0

require DiffEqBase 0.14.0

Loss Optim

Makes a general loss function for Optim.jl and MathProgBase, and builds the Jacobian via Calculus.jl or ForwardDiff.jl