Tag Stan v0.0.3 (Stan-j0.3-v0.0.3) and Jags v0.0.3 (Jags-j0.3-v0.0.3)

Bump Stan.jl tag to v0.0.3, register and tag Jags.jl v0.0.3 (Jags-j0.3-v0.0.3)