update readme

CITATION.rst

@@ -0,0 +1,16 @@
+Citation
+--------
+
+.. code-block:: latex
+
+    @misc{delhaisse2019pyrobolearn,
+        author = {Delhaisse, Brian and Xin, Songyan and Rozo, Leonel, and Caldwell, Darwin},
+        title = {PyRoboLearn: A Python Framework for Robot Learning Practitioners},
+        publisher = {GitHub},
+        journal = {GitHub repository},
+        howpublished = {\url{https://github.com/robotlearn/pyrobolearn}},
+        year=2019,
+    }
+
+
+If you use a specific learning model, algorithm, robot, controller, and so on, please cite the corresponding paper. The reference(s) can usually be found in the class documentation (at the end), and sometimes in the README file in the corresponding folder.

README.rst

@@ -197,17 +197,7 @@ PyRoboLearn is currently released under the `GNU GPLv3 <https://choosealicense.c
 Citation
 --------
 
-.. code-block:: latex
-
-    @misc{delhaisse2019pyrobolearn,
-        author = {Delhaisse, Brian and Xin, Songyan and Rozo, Leonel, and Caldwell, Darwin},
-        title = {PyRoboLearn: A Python Framework for Robot Learning Practitioners},
-        publisher = {GitHub},
-        journal = {GitHub repository},
-        howpublished = {\url{https://github.com/robotlearn/pyrobolearn}},
-        year=2019,
-    }
-
+For how to cite this repository, please refer to the ``CITATION.rst`` file.
 
 If you use a specific learning model, algorithm, robot, controller, and so on, please cite the corresponding paper. The reference(s) can usually be found in the class documentation (at the end), and sometimes in the README file in the corresponding folder.