Change README.md a bit in attempt to make pypi happy

See pypi/warehouse#4079 (comment)

Author: tomtung

README.md

@@ -108,7 +108,7 @@ pip install git+https://github.com/tomtung/omikuji.git -v
 
 The following script demonstrates how to use the Python binding to train a model and make predictions:
 
-```python
+```
 import omikuji
 
 # Train