* Add support for relationships
Adds Support for:
- Sending friend request.
- Accepting friend request.
- Getting all the relationships.
- Getting all the mutual friends with another user.
- Blocking a user.
**Note:**
- Bot accounts are not allowed to access the endpoint.
- May closebwmarrin/discordgo#150
* Implement requested changes
Changed the uint8 declarations to int.
* Change the missed unint8 declaration to int
Missed one instance of unint8 during previous push.
Renamed RateLimit struct to TooManyRequests{} and added new event struct
RateLimited{} which can be registerd to with AddHandler() and will be
emitted anytime a HTTP 429 is received on the HTTP API.
AddHandler now returns a func that can remove the handler.
The handlers map is now guarded by its own mutex.
Moved eventMap to events.go for readability.
Improved documentation.
