ALBERT tokenizer is not callable
# 🐛 Bug

## Information
when running the follwoing given example:
from transformers import AlbertTokenizer, AlbertModel
import torch
tokenizer = AlbertTokenizer.from_pretrained('albert-base-v2')
model = AlbertModel.from_pretrained('albert-base-v2')
inputs = tokenizer("Hello, my dog is cute", return_tensors="pt")

it alerts "*** TypeError: 'AlbertTokenizer' object is not callable"

examples link: https://huggingface.co/transformers/model_doc/albert.html#alberttokenizer

Model I am using (Bert, XLNet ...):
ALBERT

Language I am using the model on (English, Chinese ...):
English

The problem arises when using:
* [X ] the official example scripts: (give details below)
from transformers import AlbertTokenizer, AlbertModel
import torch
tokenizer = AlbertTokenizer.from_pretrained('albert-base-v2')
model = AlbertModel.from_pretrained('albert-base-v2')
inputs = tokenizer("Hello, my dog is cute", return_tensors="pt")
 link: https://huggingface.co/transformers/model_doc/albert.html#alberttokenizer'


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*** TypeError: 'AlbertTokenizer' object is not callable

## Expected behavior

Should given a workable example of using ALBERT ?

## Environment info
<!-- You can run the command `transformers-cli env` and copy-and-paste its output below.
     Don't forget to fill out the missing fields in that output! -->


- `transformers` version:  2.3.0
- Platform:  Linux
- Python version:   3.7.4
- PyTorch version (GPU?):   1.4.0
- Tensorflow version (GPU?):  
- Using GPU in script?:  Yes
- Using distributed or parallel set-up in script?:   No

Hi there, you should upgrade your transformers library to v3. The version you have does not have callable tokenizers.

Alternatively, the docs for v2.3.0 are [here](https://huggingface.co/transformers/v2.3.0/). You can use the dropdown menu on the left (just under the hugging face) to change the version of the documentation you are using.<|||||>Thanks very much<|||||>Alternatively,  I found using tokenizer.ecode is ok. 
But, How to view the old doc details for this version?
https://huggingface.co/transformers/v2.3.0/model_doc/albert.html#
This link seems to be archived documentation. No examples provided here.<|||||>This is the documentation of the version 2.3.0. For better documentation, you should really consider upgrading your library :-)<|||||>Understand. Thanks very much.