Won't use HTTP(S)_PROXY env var if proxy explicitly set to null.

request.js

@@ -141,7 +141,7 @@ Request.prototype.init = function (options) {
     self.rejectUnauthorized = false
   }
 
-  if(!self.proxy) {
+  if(!self.hasOwnProperty('proxy')) {
     // check for HTTP(S)_PROXY environment variables
     if(self.uri.protocol == "http:") {
         self.proxy = process.env.HTTP_PROXY || process.env.http_proxy || null;

tests/test-proxy-null.js

@@ -0,0 +1,39 @@
+var server = require('./server')
+  , events = require('events')
+  , stream = require('stream')
+  , assert = require('assert')
+  , fs = require('fs')
+  , request = require('../index')
+  , path = require('path')
+  , util = require('util')
+  ;
+
+var port = 6768
+  , called = false
+  , proxiedHost = 'google.com'
+  ;
+
+// set up environment variable
+process.env.HTTP_PROXY = 'http://localhost:'+port;
+
+var s = server.createServer(port)
+s.listen(port, function () {
+  s.on('http://google.com/', function (req, res) {
+    called = true
+    assert.equal(req.headers.host, proxiedHost)
+    res.writeHeader(200)
+    res.end()
+  })
+  request ({
+    url: 'http://'+proxiedHost,
+    // should not read from HTTP_PROXY env var
+    proxy: null,
+    timeout: 500,
+  }, function (err, res, body) {
+    s.close()
+  })
+})
+
+process.on('exit', function () {
+  assert.ok(!called, 'the request must not be made to the proxy server')
+})