Twit 02 Retrieve user twitter home stream

Creates a generic parser and requester. Performing a request against the REST api now requires the correct pair. 

Example:
To request the twitter android dev stream, the request requires the TwitterObjectRequester (Twitter responds with a JsonObject) and the TweetsHashTagParser to parse the Json object.


so, one of the things that you'll discover is super annoying is when you change one part of the code, and a reviewer starts commenting not on the change you made, but something they notice just because the context is displayed too :tongue: 

in this case, I haven't had a deep look, but the `OAuthRequester` is the only thing that uses the Activity, and it's being treated as a callback, not an activity.

- the constructor shouldn't take this activity because it's not used in this class; it's only used by another object inside this class (the requestor)
- the requestor is currently instantiated inside the constructor - the requestor should be passed into the constructor as a parameter. Create the requestor inside the `newInstance()` method.
- when you create the requestor, pass the activity in as a dependency, but not as `Activity`, as whatever it expects (`Callback` I presume)