[doc] add a document to test invalid input

- #88
- also update some document

README.md

@@ -61,6 +61,7 @@ Read the [Document](http://pyswagger.readthedocs.org/en/latest/), or just go thr
 - [Exntending Primitive Factory for user-defined primitives](docs/md/tutorial/extend_prim.md)
 - [Rendering Random Requests for BlackBox Testing](docs/md/tutorial/render.md)
 - [Operation MIME Support](docs/md/tutorial/mime.md)
+- [Test with Invalid Input](docs/md/tutorial/invalid.md)
 
 ---------
 

docs/md/tutorial/invalid.md

@@ -0,0 +1,30 @@
+### Test With Invalid Input
+
+All you provided for **pyswagger.spec.v2_0.objects.Operation** would be inspected / validated based on the loaded Swagger (OpenAPI) spec. Therefore, when using pyswagger as an API client, this behavior is relevant, but it's just not required when you want to provide some invalid input for your own server.
+
+Can those validation be skipped? No, but pyswagger allows you to patch them after "prepared". Taking an example from this [issue](https://github.com/mission-liao/pyswagger/issues/88)
+
+```python
+from pyswagger import App
+from pyswagger.contrib.client.requests import Client
+
+app = App._create_('http://petstore.swagger.io/v2/swagger.json')
+client = Client()
+
+pet_tom = dict(
+    id=123,
+    name='Tom',
+    photoUrls='https://github.com/',
+    status='available')                                                                                       
+
+req, resp = app.op['addPet'](body=pet_tom) 
+
+#  patching the "body" parameter named "body", ... which seems cumbersome
+req._p['body']['body']['id'] = 'not_valid'
+
+resp = client.request((req, resp,))                                                                            
+print resp.status # the code I tried is 500, not 405
+```
+
+You can access those "prepared" parameters via **pyswagger.io.Request._p** property, it's a *dict*, which is arranging the parameters you provided by "type" and "name" defined in [OpenAPI spec](https://github.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md#parameter-object). To be noted: when the name of "type" changed in later version of OpenAPI, **the key of _p would also be changed**.
+

pyswagger/io.py

@@ -211,15 +211,15 @@ def prepare(self, scheme='http', handle_files=True, encoding='utf-8'):
 
     @property
     def url(self):
-        """ url of this request
+        """ url of this request, only valid after 'prepare'
 
         :type: str 
         """
         return self.__url
 
     @property
     def path(self):
-        """ path of this request
+        """ path of this request, only valid after 'prepare'
 
         :type: str
         """
@@ -251,15 +251,15 @@ def method(self):
 
     @property
     def header(self):
-        """ header of this request
+        """ header of this request, only valid after 'prepare'
 
         :type: dict
         """
         return self.__header
 
     @property
     def data(self):
-        """ data carried by this request
+        """ data carried by this request, only valid after 'prepare'
 
         :type: byte
         """