Update README.md

Author: hpyhacking

README.md

@@ -19,7 +19,7 @@ Help is greatly appreciated, feel free to submit pull-requests or open issues.
 
 ### Things You Should Know ###
 
-RUNNING A EXCHANGE IS HARD.
+RUNNING AN EXCHANGE IS HARD.
 
 Peatio makes it easier, but running an exchange is still harder than a blog, which you can download the source code and following the guide or even a cool installer and boom!!! a fancy site is there to profit. We always prioritize security and speed higher than 1-click setup. We split Peatio to many components (processes) so it's flexible to deploy and scalable.