Feature request: support min/max range for Float/Int

[cxong]

Example usage:

>>>import strictyaml as sy
>>>schema = sy.Map({"foo": sy.Float(minimum=0, maximum=0.1)})
>>>sy.as_document({"foo": 0.2}, schema)
...
strictyaml.exceptions.YAMLSerializationError: when expecting a float in the range [0, 0.1], got 0.2

If there are no objections I could try creating a PR

[crdoconnor]

No objections. Please just remember to write the story first and then make it pass. If you have any trouble setting up the test environment just let me know.

[crdoconnor]

Is this going ok, @cxong ? Do you need any help?

[cxong]

Sorry for the delay; I briefly looked at it earlier but I haven't used hitch before and got stuck somewhere. I'll take a look again when I have time.