Add a build step and produce ES6 files.

[givanse]

This PRs does the following:

• convert to TypeScript pretender.js => src/index.ts
  • the rollup config outputs the files:
    • pretender.js - this is the IIFE version, it should be working the same as before
    • pretender.es.js - this one is new
• replace jscs with eslint (jscs merged with eslint)
• bump the supported node versions
• started using Yarn
• depends on add module attribute FakeXMLHttpRequest#46

I'm still testing this with an actual app, but I think its ready to get reviewed and get a conversation started. done with that

• simple repo that showcases usage: https://github.com/givanse/use-pretender-as-a-module
• tested with ember-cli-mirage (yarn link pretender)
• tested it with a brand new glimmer app (0.13.0)

[givanse]

Took the liberty of bumping the version number since this is a fairly large change to the code base.

[givanse]

TS is working

[givanse]

Pretender imported as a ES6 module. Also not that this test file is a ts file.

[givanse]

For the repo linked here, I added as collaborators the people that have merge access to Pretender.

Or if you prefer me to delete the mention of 'use-pretender-as-a-module', that is fine, I will.

[mike-north]

Is there any reason why all of these

• convert to TypeScript pretender.js => src/index.ts
  • the rollup config outputs the files:
    • pretender.js - this is the IIFE version, it should be working the same as before
    • pretender.es.js - this one is new
• replace jscs with eslint (jscs merged with eslint)
• bump the supported node versions
• started using Yarn

must be included in a single PR? I could see this being at least 4

1. use yarn
2. jscs -> eslint
3. es module conversion (changing existing tests as little as possible, in order to prove that this is purely a packaging change)
4. ts conversion (it's nearly always a better idea to do this as an independent PR, to ensure that the code change only adds type information without modifying runtime behavior in any breaking way)

This also has the potential to be a minor release.

[givanse]

you are right, this got too messy, I'll split it up

[givanse]

PR #243

Add build step and TS support