don't require callback for synchronous identify functions

[noam3127]

Perhaps this is just a personal preference, but I believe that callbacks should only be required for functions that may perform asynchronous operations. For all synchronous functions, requiring a callback to be passed in may mislead devs into thinking that it's asynchronous and requires unnecessary consideration for control flow. Therefore, I made the callbacks optional for bot.identifyBot() and bot.identifyTeam() because there's absolutely nothing async taking place in those.

[anonrig]

It's a good approach when using yield on ES6, but if you're not using it, it gives a synchronous feeling to a asynchronous function.

[benbrown]

I will allow it! Thanks.