Bump Stan.jl to version v"0.1.0"

The two most important features introduced in version 0.1.0 are:

1. Using Mamba to display and diagnose simulation results. The call to
stan() to sample now returns a Mamba Chains object (previously it
returned a dictionary).
2. The ability to select which variables to extract form Stan's output
.csv file(s).
Merge pull request #1675 from goedman/metadata-v2

Bump Stan.jl to version v"0.1.0"