title: grequests with requests has collision
body: <p>I am using grequests python module to call some APIs. I want to make two functions. </p>
  
  <ol>
  <li>A single request(use requests module)</li>
  <li>A multiple request(use grequests module)</li>
  </ol>
  
  <p>When I use two modules in two different files, it runs normally, but when I import two modules in the same file, requests module fall in infinity recursive.</p>
  
  <pre><code>  #!/usr/bin/env python                                                                                                                                                                                          
    #-*- encoding:utf-8 -*-                                                                                                                                                                                        
  
    import requests                                                                                                                                                                                                
    import grequests                                                                                                                                                                                               
  
    def SingleRequest():                                                                                                                                                                                           
        rs = requests.get("www.example.com")                                                                                                                                                                          
        return rs                                                                                                                                                                                             
  
    def MultiRequest():                                                                                                                                                                                            
        urls = [                                                                                                                                                                                                   
            "www.example1.com", 
            "www.example2.com",  
            "www.example3.com"                                                                                                
        ]                                                                                                                                                                                                          
        rs = [grequests.get(u) for u in urls]                                                                                                                                                        
        rs_map = grequests.map(rs);                                                                                                                                                                                
        return rs_map;       
  </code></pre>
  
  <p>If I call MultiRequest() -> do Well!</p>
  
  <p>but if I call SingleRequest() ..... ↓ </p>
  
  <pre><code>Exception Type: RecursionError
  Exception Value: maximum recursion depth exceeded
  Exception Location: /usr/local/lib/python3.6/ssl.py in options, line 459
  
  /usr/local/lib/python3.6/ssl.py in options
       super(SSLContext, SSLContext).options.__set__(self, value) X 100 times...
  </code></pre>
  
  <p>Is it possible to use requests and <strong>grequests</strong> in one file?</p>