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.

sanic/router.py

@@ -18,7 +18,7 @@ Parameter = namedtuple("Parameter", ["name", "cast"])
 REGEX_TYPES = {
     "string": (str, r"[^/]+"),
     "int": (int, r"-?\d+"),
-    "number": (float, r"-?[0-9\\.]+"),
+    "number": (float, r"-?(?:\d+(?:\.\d*)?|\.\d+)"),
     "alpha": (str, r"[A-Za-z]+"),
     "path": (str, r"[^/].*?"),
     "uuid": (