Bibtex reference in README is updated.

Author: shtaxxx

README.md

@@ -30,7 +30,7 @@ If you use Pyverilog in your research, please cite my paper.
 title={Pyverilog: A Python-Based Hardware Design Processing Toolkit for Verilog HDL},
 author={Takamaeda-Yamazaki, Shinya},
 booktitle={Applied Reconfigurable Computing},
-month={Apr}
+month={Apr},
 year={2015},
 pages={451-460},
 volume={9040},

README.rst

@@ -32,7 +32,7 @@ If you use Pyverilog in your research, please cite my paper.
     title={Pyverilog: A Python-Based Hardware Design Processing Toolkit for Verilog HDL},
     author={Takamaeda-Yamazaki, Shinya},
     booktitle={Applied Reconfigurable Computing},
-    month={Apr}
+    month={Apr},
     year={2015},
     pages={451-460},
     volume={9040},