Since Record had been removed from next, some api names should be updated

[kaojohnny]

Ref: SkygearIO/features#254

Names are:

• currentUser: User
• async changePassword(oldPassword: String, newPassword: String, invalidate: Boolean): Promise
• async fetchUserRole(users: User[] | String[]): Promise
• async login(loginIDs: Object, password: String): Promise
• async loginWithEmail(email: String, password: String): Promise
• async loginWithProvider(provider: String, loginIDs: Object): Promise
• async loginWithUsername(username: String, password: String): Promise
• async signup(loginIDs: Object, password: String, data: Object): Promise
• async signupAnonymously(): Promise
• async signupWithEmail(email: String, password: String, data: Object): Promise
• async signupWithUsername(username: String, password: String, data: Object): Promise
• async whoami(): Promise