Changed rate coefficient test to use rtol

kineticsSurfaceTest used atol for rate coefficient
tests previously. The atol was too strict for
double precision floating point. All other rate
coefficient tests used rtol.

test/rmgpy/kinetics/kineticsSurfaceTest.py

@@ -741,9 +741,11 @@ def test_get_rate_coefficient(self):
                 Ea = Ea_ox - (alpha_ox * electrons_ox * constants.F * (V-V0_ox))
                 k_oxidation = A_ox * (T / T0_ox) ** n_ox * np.exp(-Ea / (constants.R * T)) 
                 Ea = Ea_red - (alpha_red * electrons_red * constants.F * (V-V0_red))
-                k_reduction = A_red * (T / T0_red) ** n_red * np.exp(-Ea / (constants.R * T)) 
-                assert round(abs(k_oxidation-self.surfchargerxn_oxidation.get_rate_coefficient(T,V)), 7) == 0
-                assert round(abs(k_reduction-self.surfchargerxn_reduction.get_rate_coefficient(T,V)), 7) == 0
+                k_reduction = A_red * (T / T0_red) ** n_red * np.exp(-Ea / (constants.R * T))
+                kox =  self.surfchargerxn_oxidation.get_rate_coefficient(T,V)
+                kred = self.surfchargerxn_reduction.get_rate_coefficient(T,V)
+                assert abs(k_oxidation - kox) < 1e-6 * kox
+                assert abs(k_reduction - kred) < 1e-6 * kred
 
     def test_change_v0(self):