make cmd non-blocking

[coltorl]

Addresses #41

[yujinyuz]

I also tested this and seems like a good solution.

But the only problem so far is that if the API responds too long, it immediately shows the results of an old request

[gorillamoe]

@coltorl @yujinyuz , thanks for helping to make kulala really nice. I fixed the issue that @yujinyuz reported. I think we're good to go. Let's push it to production :)