Add NonDictModel class

[mlyundin]

Please review. I have found that this is useful using schematics for validation of json data. According to json specification we can have not only 'dict' on top level.

[bintoro]

What specification? The JSON specification certainly allows objects at the top level.

I can't help thinking there must a better solution to the problem you're facing. While this isn't mergeable as such, we can look into the actual issue if you can provide more information.

[mlyundin]

From http://www.json.org/
In JSON, they take on these forms:
An object is an unordered set of name/value pairs.
An array is an ordered collection of values.

In my work I have faced with REST responses with json data as array on top level

[bintoro]

If you only wish to validate, say, a list of integers, you can simply use a standalone field:

>>> field = ListType(IntType)
>>> field.validate([1, 2, "3", 4])
[1, 2, 3, 4]

You don't need a containing model to do this.