Add async/await support

[flying-sheep]

I split this into two commits, because the second one is a rather mechanical addition of async: false to every single fixture containing a function (=almost all)

(fixes #119)

[eslintbot]

Thanks for the pull request, @flying-sheep! I took a look to make sure it's ready for merging and found some changes are needed:

• The commit summary needs to begin with a tag (such as Fix: or Update:). Please check out our guide for how to properly format your commit summary and update it on this pull request.

• Pull requests with code require an issue to be mentioned at the end of the commit summary, such as (fixes #1234). Please update the commit summary with an issue (file a new issue if one doesn't already exist).

Can you please update the pull request to address these?

(More information can be found in our pull request guide.)

[eslintbot]

LGTM

[flying-sheep]

travis failure is due to #128

please fix travis or ensure manually that my tests run with TypeScript 2.0.10.

I beg you to merge this quickly so that I don’t have to adapt this to every unit test change merged before this.

[JamesHenry]

I'm sure you can appreciate that the week before Christmas is exceptionally busy. Rest assured, I will be looking at this as soon as possible.

[flying-sheep]

oh, of course! i don’t want to pressure you, is just wanted to ask you to consider fast-tracking this to get in before other PRs or changes

[JamesHenry]

Thanks a lot for your patience on this, @flying-sheep! Once #131 gets merged you can rebase this

[JamesHenry]

It's in! Please rebase the PR and we'll see where we're at 😄

[eslintbot]

LGTM

[flying-sheep]

@JamesHenry done!

[JamesHenry]

Thanks a lot, glad to see that addressed the failing tests!

Given that they both touch a lot of existing assertions around functions, I think it might be sensible to hold off on this PR just until this other one gets resolved: #124

Shouldn't take too much longer!

[JamesHenry]

The other PR ended up being more isolated than it first appeared.

This LGTM, thanks a lot!

[flying-sheep]

great, thanks! sorry again for sounding pushy, y’all’re doing a great job here!