Update README.md

update citation block
add twitter shield

README.md

@@ -5,6 +5,7 @@
 [![PyPiDownloads](https://pepy.tech/badge/torch-discounted-cumsum)](https://pepy.tech/project/torch-discounted-cumsum)
 [![License](https://img.shields.io/badge/License(code)-BSD%203--Clause-blue.svg)](LICENSE_code)
 [![License: CC BY 4.0](https://img.shields.io/badge/License(doc)-CC%20BY%204.0-lightgrey.svg)](LICENSE_doc)
+[![Twitter Follow](https://img.shields.io/twitter/follow/AntonObukhov1?style=social&label=Subscribe!)](https://twitter.com/antonobukhov1)
 
 <img src="doc/img/logo_small.png" align="left" width="33%">
 
@@ -178,9 +179,9 @@ To cite this repository, use the following BibTeX:
 
 ```
 @misc{obukhov2021torchdiscountedcumsum,
-    author = {Anton Obukhov},
-    year = 2021,
-    title = {Fast discounted cumulative sums in PyTorch},
-    url = {www.github.com/toshas/torch-discounted-cumsum}
+  author={Anton Obukhov},
+  year=2021,
+  title={Fast discounted cumulative sums in PyTorch},
+  url={https://github.com/toshas/torch-discounted-cumsum}
 }
 ```