doc: added annotations about the compatibilities for blocking phase

Author: tokers

README.markdown

@@ -5,6 +5,10 @@ lua-resty-requests - Yet Another HTTP Library for OpenResty.
 
 ![Build Status](https://travis-ci.org/tokers/lua-resty-requests.svg?branch=master)
 
+```bash
+resty -e 'print(require "resty.requests".get("https://github.com", { stream = false}).content)'
+```
+
 Table of Contents
 =================
 
@@ -35,6 +39,11 @@ Status
 
 This Lua module now can be considered as production ready.
 
+Note since the `v0.7.1` release, this module started using lua-resty-socket,
+for working in the non-yieldable phases, but still more efforts are needed,
+so **DONOT** use it in the `init` or `init_worker` phases (or other
+non-yieldable phases).
+
 Features
 ========