Added support for PynamoDB up to version 3.3

Added support for PynamoDB up to version 3.3 and fixed the examples to include a more recent version of Flask.

Final Final 1.X release

• Fixes #12

Final 1.x graphene release

• Added List and Map Attribute support
• Fixed graphql-core/graphene version to < 2.x

0.9.0

• Replaced the custom List attribute used for OneToMany relationships with the newly added PynamoDB List support.
• Added ID! for strings if hash keys.

0.8.1

A PynamoDB integration for Graphene.

This release improved upon the lazy loading of the relationships implementation by replacing the previous set by a list type which preserves order of keys (the set didn't).