Change example

[ernst545]

In this example class Meta should be changed to class Index

class BlogIndex(DocType):
    pk = Integer()
    title = Text(fields={'raw': Keyword()})
    created_at = Date()
    body = Text()
    tags = Keyword(multi=True)
    is_published = Boolean()

    class Meta:
        index = 'blog'

This api has changed in the previous release of elasticsearch-dsl-py:

class Index:
    name = 'blog'

[josemlp91]

@ernst545 updated!