Returns all the documents with the specified tag.

def all_docs_with_tag(self, doc_tag):
        """
        Returns all the documents with the specified tag.
        """
        docs = []

        while True:
            try:
                doc = self.next_doc_with(doc_tag)
                docs.append(doc)

            except StopIteration:
                break

        self.seek(0)
        return docs