Please update README with latest version for rebar3 config

I just spent a good hour debug old code because I was using v1.2.0 (as per README) instead of the latest release 1.14.4 - very confusing and frustrating :(

Author: gorenje

README.md

@@ -354,7 +354,7 @@ Add to `rebar.config`
 
 ```erlang
 ...
-{deps, [{emqtt, {git, "https://github.com/emqx/emqtt", {tag, "v1.2.0"}}}]}.
+{deps, [{emqtt, {git, "https://github.com/emqx/emqtt", {tag, "1.14.4"}}}]}.
 ...
 ```