Add vocabulary fixtures for tests

tests/fixtures/small_vocabulary/.lock

tests/fixtures/small_vocabulary/animals.txt

tests/fixtures/small_vocabulary/non_padded_namespaces.txt

tests/fixtures/small_vocabulary/slices.json

tests/fixtures/train_vocabulary/.lock

tests/fixtures/train_vocabulary/deprel_labels.txt

tests/fixtures/train_vocabulary/feats_labels.txt

tests/fixtures/train_vocabulary/lemma_characters.txt

tests/fixtures/train_vocabulary/non_padded_namespaces.txt

tests/fixtures/train_vocabulary/slices.json

tests/fixtures/train_vocabulary/token_characters.txt

tests/fixtures/train_vocabulary/upostag_labels.txt

tests/fixtures/train_vocabulary/xpostag_labels.txt