Wit integration into FB chatbot

[shashankpr]

Basic implementation of Wit.ai integrated into FB chatbot and working. Related to #2

@leochirag : Once check and test it on the FB page/messenger. If the following issues are not there then accept the pull request :

Check for these Issues:

• [x] Continuous loop of messages

• [x] Wrong identification of intent or location.

Create new issue for possible enhancements and list them there.

[shashankpr]

The screenshot is attached here: