update version to 2.1

Author: ploy-np

README.md

@@ -41,7 +41,7 @@ Please refer to the github release history for previous releases: https://github
 
 ### Citing xPore
 
-If you use xPore in your research, please cite
+If you use xPore in your research, please cite 
 
 Ploy N. Pratanwanich, et al. Identification of differential RNA modifications from nanopore direct RNA sequencing with xPore. *Nat Biotechnol* (2021), [https://doi.org/10.1038/s41587-021-00949-w](https://doi.org/10.1038/s41587-021-00949-w).