Added a callAsync method

[cluelesscamel]

A pull request for a callAsync method we have been using internally for a while now.
It should be noted that the callback on Meteor.applyAsync will probably disappear in time and this is only going to work until it does.

This implementation checks all of the boxes for our needs:

• Will catch stub errors as promise rejections and keep the server from running the method if it does
• Will correctly mark a method as no longer running when its promise has been returned to allow for chaining of multiple async methods
• Will not log Exception while running simulation to the browser
• Will not throw Access denied errors in the browser by using Meteor.applyAsync

[CLAassistant]

All committers have signed the CLA.

[StorytellerCZ]

@Grubba27 I think this is ready to be merged.

[Grubba27]

Sure! Are you able to make the release?

[StorytellerCZ]

@Grubba27 No, this is under the mdg namespace.

[Grubba27]

done! published under the 1.3.0 namespace