Add logic to make dynamic route merging work

This is by no means the final solution but it's a start in the right
direction. Eventually what needs to happen is we need to reduce the
complexity of the routing. CompsitionView can probably be removed later
on in favor of better Route objects. Also in the next version of sanic
we need to move merge_route and add_parameter out of the add_route logic
and just have them as standalone methods.

The tests should cover everything that we need so that if any changes
are made we can identify regression.

sanic/router.py

@@ -149,7 +149,22 @@ class Router:
                 handler=view, methods=methods.union(route.methods))
             return route
 
-        route = self.routes_all.get(uri)
+        if parameters:
+            # TODO: This is too complex, we need to reduce the complexity
+            if properties['unhashable']:
+                routes_to_check = self.routes_always_check
+                ndx, route = self.check_dynamic_route_exists(
+                    pattern, routes_to_check)
+            else:
+                routes_to_check = self.routes_dynamic[url_hash(uri)]
+                ndx, route = self.check_dynamic_route_exists(
+                    pattern, routes_to_check)
+            if ndx != -1:
+                # Pop the ndx of the route, no dups of the same route
+                routes_to_check.pop(ndx)
+        else:
+            route = self.routes_all.get(uri)
+
         if route:
             route = merge_route(route, methods, handler)
         else:
@@ -165,6 +180,14 @@ class Router:
         else:
             self.routes_static[uri] = route
 
+    @staticmethod
+    def check_dynamic_route_exists(pattern, routes_to_check):
+        for ndx, route in enumerate(routes_to_check):
+            if route.pattern == pattern:
+                return ndx, route
+        else:
+            return -1, None
+
     def remove(self, uri, clean_cache=True, host=None):
         if host is not None:
             uri = host + uri