Updated README

README.md

@@ -5,4 +5,8 @@
 [![Code Coverage](https://codecov.io/gh/AlgebraicJulia/AlgebraicPetri.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/AlgebraicJulia/AlgebraicPetri.jl)
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-Build petri net agent based models compositionally
+`AlgebraicPetri.jl` is a Julia library for building Petri net agent based models
+compositionally. This library acts as a bridge between
+[Catlab.jl](https://github.com/AlgebraicJulia/Catlab.jl) and
+[Petri.jl](https://github.com/mehalter/Petri.jl). This package defines the
+category of Open Petri Nets as described in [[Baez 2018](https://arxiv.org/abs/1808.05415)].