Fixing a bug where long tokenizer files would be incorrectly deserialized (#459)

* Fixing a bug where long tokenizer files would be incorrectly
deserialized

- Add a bunch of tests to check deserialization behaviour
- One tests also confirms current Single deserialization of Sequence.

* Better test locations for Windows + no file dependency in Python binding
Rust side.

* Adressing @n1t0 comments.

bindings/python/tests/test_serialization.py

@@ -0,0 +1,10 @@
+from tokenizers import Tokenizer, models, normalizers
+from .utils import data_dir, albert_base
+
+
+class TestSerialization:
+    def test_full_serialization_albert(self, albert_base):
+        # Check we can read this file.
+        # This used to fail because of BufReader that would fail because the
+        # file exceeds the buffer capacity
+        tokenizer = Tokenizer.from_file(albert_base)