add asyncCall as an action parameter,

[FredericHeem]

The idea behind this PR is to avoid calling directly listenAndPromise, instead, pass the function as a new action parameter asyncCall
Before:

let actions = Reflux.createActions({
    signupOrLoginThirdParty: { asyncResult: true },
    signupLocal: { asyncResult: true }
} );

actions.signupOrLoginThirdParty.listenAndPromise( auth.signupOrLoginThirdParty );
actions.signupLocal.listenAndPromise( auth.signupLocal );

After:

let actions = Reflux.createActions({
    signupOrLoginThirdParty: { asyncCall:  auth.signupOrLoginThirdParty },
    signupLocal: { asyncCall: auth.signupLocal }
} );

[devinivy]

Minus the .only()

[devinivy]

Given that promise support is broken out into the reflux-promise project, we'll have to figure out if this feature is suitable for reflux-core. I definitely do see why this feature may be desirable, but it needs to be balanced against keeping a fairly simple, not-too-too-magical core. In any case thanks for the contribution! We'll try to figure it out soon. CC @spoike @benglass.

[FredericHeem]

Thanks for the catch, the .only has been removed.

[FredericHeem]

Any news on that PR ?