Add test cases for the proxy, and do some tiny fixes.

the fixes are:
1. add "content-type" in headers for when dealing with localresponse
2. make a more accurate tip for throttle rate when lower than 1
3. make the crtMgr funcionality a more independent one
4. uppercase the request header before sending it out

update the tip

test/util/ProxyServerUtil.js

@@ -0,0 +1,65 @@
+/*
+* Utility class for creating proxy server, used to create specfied proxy server
+*
+*/
+
+let proxy = require('../../proxy.js');
+const util = require('../../lib/util.js');
+
+const DEFAULT_OPTIONS = {
+    type: "http",
+    port: 8001,
+    hostname: "localhost",
+    dbFile: null,  // optional, save request data to a specified file, will use in-memory db if not specified
+    webPort: 8002,  // optional, port for web interface
+    socketPort: 8003,  // optional, internal port for web socket, replace this when it is conflict with your own service
+    throttle: 10000,    // optional, speed limit in kb/s
+    disableWebInterface: false, //optional, set it when you don't want to use the web interface
+    setAsGlobalProxy: false, //set anyproxy as your system proxy
+    interceptHttps: true, // intercept https as well
+    silent: false //optional, do not print anything into terminal. do not set it when you are still debugging.
+};
+
+/**
+*
+* @return An instance of proxy, could be closed by calling `instance.close()`
+*/
+function defaultProxyServer () {
+    proxy = util.freshRequire('../proxy.js');
+
+    const options = util.merge({}, DEFAULT_OPTIONS);
+    options.rule = util.freshRequire('./rule_default.js');
+    return new proxy.proxyServer(options);
+}
+
+/*
+* Create proxy server with rule
+* @param rules
+    Object, the rule object which contains required intercept method
+  @return An instance of proxy, could be closed by calling `instance.close()`
+*/
+function proxyServerWithRule (rule) {
+    proxy = util.freshRequire('../proxy.js');
+
+    const options = util.merge({}, DEFAULT_OPTIONS);
+    options.rule = rule;
+
+    return new proxy.proxyServer(options);
+}
+
+function proxyServerWithoutHttpsIntercept (rule) {
+    proxy = util.freshRequire('../proxy.js');
+
+    const options = util.merge({}, DEFAULT_OPTIONS);
+    if (rule) {
+        options.rule = rule;
+    }
+    options.interceptHttps = false;
+    return new proxy.proxyServer(options);
+}
+
+module.exports = {
+    defaultProxyServer,
+    proxyServerWithoutHttpsIntercept,
+    proxyServerWithRule
+};