PyCharm autocompletion for properties

Due to the fact that the classes have dynamically generated fields for the AWS resource properties, IDEs like PyCharm doesn't suggest those fields during autocompletion.

For example:
```Python
from troposphere import Template, apigateway

t = Template()

apiResource = apigateway.Resource("contactcloud")
apiResource.ParentId #<-- won't be suggested by autocompletion!
```

This could be remedied in two ways:

### 1. Add type hints to the beginning of classes, e.g.:
```Python
class Resource(AWSObject):
ParentId: basestring # Python 3 type hints for fields
PathPart: basestring
RestApiId: basestring

resource_type = "AWS::ApiGateway::Resource"

props = {
"ParentId": (basestring, True),
"PathPart": (basestring, True),
"RestApiId": (basestring, True)
}
```

### 2. Generate stub files
This is outlined by [PEP 484#stub-files](https://www.python.org/dev/peps/pep-0484/#stub-files)