Call return value

[bigfacewo]

relate https://github.com/dollarshaveclub/postmate/pull/20.

can i do this:

postmate.call('functionName', data).then(value => {

})

If you do, the get and call APIs can be merged into call.

In some cases, I really need to execute the next call after the last call is finished. Is there any other good way to use it?