Add example of how to implement a POST request

By "sniffing" the normal request (`Page.navigate`, GET method), method,
headers and postData parameters can be modified. As this is not fairly
intuitive, I decided to add an example.

Author: Marcos

examples/post_request.py

@@ -0,0 +1,87 @@
+import pychrome
+import time
+import urllib
+
+
+
+class ChromiumClient(object):
+    """ Client to interact with Chromium """
+
+    def __init__(self):
+        self.browser = pychrome.Browser(url="http://127.0.0.1:9222")
+
+    def do_post(self):
+        self.tab = self.browser.new_tab()
+
+        event_handler = EventHandler()
+
+        event_handler.set_token('asdkflj497564dsklf')
+        event_handler.set_post_data({
+            'param1': 'value1',
+            'param2': 'value2'
+        })
+
+        url_pattern_object = {'urlPattern': '*fate0*'}
+        self.tab.Network.setRequestInterception(patterns=[url_pattern_object])
+
+        self.tab.Network.requestIntercepted = event_handler.on_request_intercepted
+
+        self.tab.start()
+
+        self.tab.Network.enable()
+        self.tab.Page.enable()
+
+        self.tab.Page.navigate(url='https://github.com/fate0/pychrome')
+
+        self.tab.wait(5)
+        self.tab.stop()
+
+        self.browser.close_tab(self.tab.id)
+
+
+class EventHandler(object):
+    def __init__(self):
+        self.tab = None
+        self.token = None
+        self.is_first_request = False
+        self.post_data = {}
+
+    def set_tab(self, t):
+        self.tab = t
+
+    def set_token(self, t):
+        self.token = t
+
+    def set_post_data(self, pd):
+        self.post_data = pd
+
+    def on_request_intercepted(self, **kwargs):
+        new_args = {'interceptionId': kwargs['interceptionId']}
+
+        if self.is_first_request:
+            # Modify first request only, following are media/static
+            # requests...
+            self.is_first_request = False
+
+            extra_headers = {
+                'Requested-by': 'Chromium',
+                'Authorization': 'Token ' + self.token
+            }
+
+            request = kwargs.get('request')
+            request['headers'].update(extra_headers)
+
+            new_args.update({
+                'url': request['url'],
+                'method': 'POST',
+                'headers': request['headers'],
+                'postData': urllib.urlencode(self.post_data)
+            })
+
+        self.tab.Network.continueInterceptedRequest(**new_args)
+
+
+if __name__ == '__main__':
+    client = ChromiumClient()
+
+    client.do_post()