Added note about requiring R14. Closes wooga#2.

README.md

@@ -26,6 +26,8 @@ EUnit tests:
 
     ./rebar eunit
 
+Eredis uses the `binary` module which was introduced in R14.
+
 ## Commands
 
 Eredis has only one function to interact with redis, which is
@@ -124,4 +126,4 @@ bulk at once.
 Although this project is almost a complete rewrite, many patterns are
 the same as you find in Erldis, most notably the queueing of requests.
 
-`create_multibulk/1` and `to_binary/1` were taken verbatim from Erldis.
+`create_multibulk/1` and `to_binary/1` were taken verbatim from Erldis.