stop number route accepting excess '.'s

We stop getting:

    ValueError: could not convert string to float: '12.34.56'

when passing 12.34.56 as a number route parameter argument.
By accepting ".12" and "12.", this is a non-breaking change. All valid
floats described by [0-9\.]+ are still accepted, just invalid ones are
now rejected.

tests/test_routes.py

@@ -365,9 +365,18 @@ def test_dynamic_route_number(app):
     request, response = app.test_client.get("/weight/1234.56")
     assert response.status == 200
 
+    request, response = app.test_client.get("/weight/.12")
+    assert response.status == 200
+
+    request, response = app.test_client.get("/weight/12.")
+    assert response.status == 200
+
     request, response = app.test_client.get("/weight/1234-56")
     assert response.status == 404
 
+    request, response = app.test_client.get("/weight/12.34.56")
+    assert response.status == 404
+
 
 def test_dynamic_route_regex(app):
     @app.route("/folder/<folder_id:[A-Za-z0-9]{0,4}>")
@@ -672,9 +681,18 @@ def test_dynamic_add_route_number(app):
     request, response = app.test_client.get("/weight/1234.56")
     assert response.status == 200
 
+    request, response = app.test_client.get("/weight/.12")
+    assert response.status == 200
+
+    request, response = app.test_client.get("/weight/12.")
+    assert response.status == 200
+
     request, response = app.test_client.get("/weight/1234-56")
     assert response.status == 404
 
+    request, response = app.test_client.get("/weight/12.34.56")
+    assert response.status == 404
+
 
 def test_dynamic_add_route_regex(app):
     async def handler(request, folder_id):