v0.2.3

StockFlow v0.2.3

Diff since v0.2.2

Merged pull requests:

• Causal loop compose (#124) (@neonWhiteout)
• Change Graph to GraphSF to not interfere with Catlab Graph. (#125) (@neonWhiteout)
• Causal Loop with Polarities (#128) (@neonWhiteout)
• System structure causal loop convert test (#130) (@neonWhiteout)
• Removing spurious dependency on GraphViz.jl (#131) (@KevinDCarlson)
• Run notebook examples in CI (#132) (@Saityi)