Merge pull request #243 from excfergodst/patch-1

Update USAGE.md with one period

Author: thinkingserious

USAGE.md

@@ -495,7 +495,7 @@ If the API Key ID does not exist an HTTP 404 will be returned.
   ```
 ## Delete API keys
 
-**This endpoint allows you to revoke an existing API Key**
+**This endpoint allows you to revoke an existing API Key.**
 
 Authentications using this API Key will fail after this request is made, with some small propogation delay.If the API Key ID does not exist an HTTP 404 will be returned.