add more undirected graph families: distance-regular (#16)

Author: nsajko

src/GraphProperties.jl

@@ -115,6 +115,9 @@ let
         (:GraphIsTriangleFree, "Is an undirected graph *triangle-free*?"),
         (:GraphIsComplete, "Is an undirected graph *complete*?"),
         (:GraphIsRegular, "Is an undirected graph *regular*?"),
+        (:GraphIsDistanceRegular, "Is an undirected graph *distance-regular*?"),
+        (:GraphIsDistanceTransitive, "Is an undirected graph *distance-transitive*?"),
+        (:GraphIsStronglyRegular, "Is an undirected graph *strongly regular*?"),
         (:GraphIsPerfect, "Is an undirected graph *perfect*?"),
         (:GraphIsTriviallyPerfect, "Is an undirected graph *trivially perfect*?"),
         (:GraphIsModular, "Is an undirected graph *modular*?"),