Small patch for the method get_reactive_scheme in reaction_set and
a method to inquire if the reaction is reversible or not in reaction.h
Tests for reactive scheme added, and in reaction_set.h some formatting
bettering (i.e. netRates -> net_rates)
Merge pull request #30 from SylvainPlessis/patch_irr

Small patch for the method get_reactive_scheme in reaction_set and