Refactor: Change reachability interfaces to handle multiple removals/insertions

include/algorithm/decremental_reachability.h

@@ -18,7 +18,7 @@ public:
   virtual bool query(const T& u, const T& v) =0;
 
   // Remove edge e(u,v) and maintain the transitive closure matrix
-  virtual void remove(const T& u, const T& v) =0;
+  virtual void remove(const std::vector<std::pair<T, T>>& edges) =0;
 protected:
   Digraph<T> G;
 };