dev(hansbug): Do some update in requirements && add api_doc page and installation_check page

docs/source/api_doc/config/index.rst

+treetensor.config
+=====================
+
+.. toctree::
+    :maxdepth: 3
+
+    meta

docs/source/api_doc/config/meta.rst

+treetensor.config.meta
+==========================
+
+.. automodule:: treetensor.config.meta
+
+\_\_TITLE\_\_
+------------------
+
+.. autodata:: treetensor.config.meta.__TITLE__
+    :annotation:
+
+
+\_\_VERSION\_\_
+------------------
+
+.. autodata:: treetensor.config.meta.__VERSION__
+    :annotation:
+
+
+\_\_DESCRIPTION\_\_
+----------------------
+
+.. autodata:: treetensor.config.meta.__DESCRIPTION__
+    :annotation:
+
+
+\_\_AUTHOR\_\_
+------------------
+
+.. autodata:: treetensor.config.meta.__AUTHOR__
+    :annotation:
+
+
+\_\_AUTHOR_EMAIL\_\_
+----------------------
+
+.. autodata:: treetensor.config.meta.__AUTHOR_EMAIL__
+    :annotation:

docs/source/index.rst

-.. DI-treetensor documentation master file, created by
-   sphinx-quickstart on Sun Sep  5 23:14:14 2021.
-   You can adapt this file completely to your liking, but it should at least
-   contain the root `toctree` directive.
+Welcome to DI-TreeTensor's Documentation
+================================================
+
+Overview
+-------------
+
+``DI-TreeTensor`` is a generalized tree-based tensor structure, \
+based on `treevalue <https://github.com/opendilab/treevalue>`_ \
+module.
+
+.. toctree::
+    :maxdepth: 2
+    :caption: Tutorials
+
+    tutorials/installation/index
 
-Welcome to DI-treetensor's documentation!
-=========================================
 
 .. toctree::
-   :maxdepth: 2
-   :caption: Contents:
+    :maxdepth: 2
+    :caption: API Documentation
 
+    api_doc/config/index
 
 
-Indices and tables
-==================
+.. toctree::
+    :maxdepth: 2
+    :caption: Contributor Guide
 
-* :ref:`genindex`
-* :ref:`modindex`
-* :ref:`search`

docs/source/tutorials/installation/index.rst

+Installation
+===================
+
+DI-treetensor is currently hosted on PyPI. It required python >= 3.6.
+
+You can simply install DI-treetensor from PyPI with the following command:
+
+.. code:: shell
+
+    pip install di-treetensor
+
+You can also install with the newest version through GitHub:
+
+.. code:: shell
+
+    pip install -U git+https://github.com/opendilab/DI-treetensor.git@main
+
+After installation, run this python code, and version information \
+of ``treetensor`` should be shown.
+
+.. literalinclude:: install_check.demo.py
+    :language: python
+    :linenos:
+
+.. literalinclude:: install_check.demo.py.txt
+    :language: text
+    :linenos:
+
+DI-treetensor is still under development, you can also check out the documents in stable version through `https://opendilab.github.io/DI-treetensor/ <https://opendilab.github.io/DI-treetensor/>`_.

docs/source/tutorials/installation/install_check.demo.py

+from treetensor.config.meta import __TITLE__, __VERSION__, __AUTHOR__, __DESCRIPTION__
+
+if __name__ == '__main__':
+    print(__TITLE__, __VERSION__)
+    print(__DESCRIPTION__)
+    print('Powered by', __AUTHOR__)

requirements.txt

 treevalue>=0.1.0
-numpy>=1.10
 torch>=1.3.1,<=1.8.0