v0.4.0

AbstractMCMC v0.4.0

Diff since v0.3.0

Merged pull requests:

• Simplify step!, sample_init!, and sample_end! (#11) (@devmotion)
• Change handling of transitions (#12) (@devmotion)
• Install TagBot as a GitHub Action (#14) (@JuliaTagBot)
• Do not implement methods from Base (#15) (@devmotion)