A little update for README.md.

README.md

@@ -33,7 +33,7 @@ It will return an ID of a new CAPTCHA in `text/plain`.
 Responds with an image in JPEG format (`image/jpeg`).
 
 An optional URL parameter `style=` set a name of a CAPTCHA style if it is
-supported by CAPTCHA implementation.
+supported by CAPTCHA implementation. E.g. `style=dark`.
 
 #### HTTP codes
 - `200` if exists
@@ -110,7 +110,7 @@ Get an image for a CAPTCHA:
 
     i := inmemdb.Image(captchaID, captchaStyle)
     if i == nil {
-        ... // error handling
+        ... // do something if there was no image returned
     }
 
     jpeg.Encode(w, *i, &jpeg.Options{Quality: 20})