replace with real pic

Author: bradjc

README.md

@@ -2,7 +2,7 @@ Signpost
 ========
 
 <img src="https://raw.githubusercontent.com/lab11/signpost/master/media/signpost_on_sign_full_666x1000.jpg" alt="Signpost" width="31%" align="left" />
-<img src="https://raw.githubusercontent.com/lab11/signpost/master/media/signpost_in_ann_arbor.jpg" align="left" width="63%" />
+<img src="https://raw.githubusercontent.com/lab11/signpost/master/media/signpost_close_up_662x1000.jpg" align="left" width="30%" />
 
 Modular city-scale sensing platform.