Started work on caching abilities

Added authenticate(), getSnaps() (unfinished), getFriends()
(unfinished), _setSnaps(), _getUpdates() (unfinished), getAuthToken()
and several variables.

Version updated to 0.2

SnapchatResponse’s setField() and getField() functions are now
deprecated.
To get response fields that don’t have a corresponding function, use:
```$response->getRaw()->field_name``` (WARNING: Snap are NOT formatted
in this method so please do a var_dump to get the field names)
Deprecation of setField() and getField()
README.md updated
Docs updated
Forgot to remove some debugging methods
Added _setFriends()

Also minor whitespace change in _setSnaps()
Implemented getSnaps() and getFriends()
README.md updated
Docs updated