v0.8.4

AlgebraicPetri v0.8.4

Diff since v0.8.3

Merged pull requests:

• Add utility to flatten labelled petri nets with tuples of symbols (#94) (@mehalter)
• Stratification now works with LabelledReactionNets (#95) (@olynch)
• Create Petri net with all pairwise 'identity' transformations (#96) (@epatters)
• Construct ODEProblem from a ReactionNet (#97) (@olynch)
• Pairwise identity transitions with rate parameters (#98) (@epatters)