opened
not-an-aardvark
username_0
**What is the purpose of this pull request? (put an "X" next to item)**

[ ] Documentation update
[ ] Bug fix ([template](https://github.com/eslint/eslint/blob/master/templates/bug-report.md))
[ ] New rule ([template](https://github.com/eslint/eslint/blob/master/templates/rule-proposal.md))
[ ] Changes an existing rule ([template](https://github.com/eslint/eslint/blob/master/templates/rule-change-proposal.md))
[x] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

<!--
    If the item you've checked above has a template, please paste the template questions below and answer them. (If this pull request is addressing an issue, you can just paste a link to the issue here instead.)
-->


<!--
    The following is required for all pull requests:
-->

**Please check each item to ensure your pull request is ready:**

- [x] I've read the [pull request guide](http://eslint.org/docs/developer-guide/contributing/pull-requests)
- [x] I've included tests for my change
- [x] I've updated documentation for my change (if appropriate)

**What changes did you make? (Give an overview)**

This adds a fixer for `strict`. The fixer removes unnecessary `'use strict';` directives. Other errors reported by the `strict` rule are not fixed, to avoid breaking any working code.

See also: #6668, #6856

**Is there anything you'd like reviewers to focus on?**

Nothing in particular.
Update: add fixer for `strict` (fixes #6668)
issue