Added python 2.7 support, reworked events

- Reworked events, so now they support python 2.7 (I had to remove some
functionality though, but that was a little unnecessary anyway)
- Events now support the old style of writing, for people who's more
comfortable with that: ```python
class EchoBot(fbchat.Client):
    def onMessage(self, *args, **kwargs):
        self.something(*args, **kwargs)
```
While still supporting the new method:
```python
class EchoBot(fbchat.Client):
    def __init__(self, *args, **kwargs):
         super(EchoBot, self).__init__(*args, **kwargs)
         self.onMessage += lamda *args, **kwargs: self.something(*args,
**kwargs)
```
- Included `msg` as a parameter in every event function, since it's
useful if you want to extract some of the other data
- Moved test data to the folder `tests`
- Fixed various other functions, and improved stability

tests/data.json

@@ -0,0 +1,6 @@
+{
+    "email": "",
+    "password": "",
+    "user_thread_id": "",
+    "group_thread_id": ""
+}