Allowing delocalization paths allyl to the radical center

to include a birad.
This addresses issue ReactionMechanismGenerator#545 where RMG isn't able to calculate degeneracy
since the resonance structures weren't explored for molecules like [CH]=C[N]

rmgpy/molecule/pathfinder.py

@@ -228,7 +228,7 @@ def findAllDelocalizationPaths(atom1):
     paths = []
     for atom2, bond12 in atom1.edges.items():
         # Vinyl bond must be capable of gaining an order
-        if (bond12.isSingle() or bond12.isDouble()) and atom1.radicalElectrons == 1:
+        if (bond12.isSingle() or bond12.isDouble()) and (atom1.radicalElectrons == 1 or atom1.radicalElectrons == 2):
             for atom3, bond23 in atom2.edges.items():
                 # Allyl bond must be capable of losing an order without breaking
                 if atom1 is not atom3 and (bond23.isDouble() or bond23.isTriple()):

rmgpy/molecule/pathfinderTest.py

@@ -358,3 +358,18 @@ def test_3_atoms(self):
         self.assertEquals(distances, expected)
 
 
+class FindAllDelocalizationPathsTest(unittest.TestCase):
+    """
+    test the findAllDelocalizationPaths method
+    """
+    def test_allyl_radical(self):
+        smi = "[CH2]C=C"
+        mol = Molecule().fromSMILES(smi)
+        paths = findAllDelocalizationPaths(mol.atoms[0])
+        self.assertIsNotNone(paths)
+
+    def test_nitrogenated_birad(self):
+        smi = '[CH]=C[N]'
+        mol = Molecule().fromSMILES(smi)
+        paths = findAllDelocalizationPaths(mol.atoms[0])
+        self.assertIsNotNone(paths)