[Fixed Bugs] POST /User/:user_id/Friend/:friend_id avatar error
[Fixed Bugs] Location/WhereAmI query is incorrect
[Modify] Location/WhereAmI response check_in data
[Fixed Bugs] User/:user_id/Friend/:friend_id can't add friend to user's friend list
[Modify] Change version code to v0.0.21 (Beta)
[Release] Da Village API v0.0.21 (Beta)