Restrict modifier chaining

[novemberborn]

Explicitly specify allowable chains, with some ground rules in mind:

Test chaining rules:

• serial must come at the start
• only and skip must come at the end
• failing must come at the end, but can be followed by only and skip
• only and skip cannot be chained together
• no repeating

Hook chaining rules:

• always comes immediately after "after hooks"
• skip must come at the end
• no only
• no repeating

Additionally:

• todo cannot be chained, except after serial
• hooks are not available on serial

This commit also removes now unnecessary assertions from TestCollection.

Fixes #1182.

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This allows the TypeScript definition to be simplified. I've done an initial refactor. Note that I've not included any JSDoc comments. I think we can do a lot better than we what we had before but I didn't want to sort that out just yet. Will open a follow-up ticket. I have fixed throws / notThrows taking observables. Would be nice to get a better type definition for Observable though. Will ask more explicitly in a follow-up ticket.

• Create issue for Observable typing in TS and Flow
• Create issue for embedding documentation in the TS and Flow definitions
• Create issue in eslint-plugin-ava to check chains when linting

[novemberborn]

Finished the TS refactor and did a similar one for Flow too. Also wrote some documentation for Flow, though still need to add the best way of stripping the type annotations. Will file a follow-up ticket for that too.

[novemberborn]

I've documented how to strip flow type annotations and improved typings for t.throws() and t.notThrows(). TS should be fine without explicit type hints, though Flow needs some help. I've updated the documentation to reflect this.

[sindresorhus]

ComonJS => CommonJS

[sindresorhus]

import {* as ava} from 'ava' => import * as ava from 'ava'

[sindresorhus]

Good to see this being cleaned up before the 1.0 release.

[sindresorhus]

Can you open an issue on eslint-plugin-ava about making a rule for this?

[novemberborn]

@sindresorhus Thanks. Will make the fixes and open follow-up issues. Will sneak in TypeScript 2.7 as well.

I'm considering revisiting the import {serial as test} / test.before() use-case in this PR. I think having accurate imports is more important than trying to "help". We should make serial with hooks work as expected too, and not support it before that's done.