Update package requirements

Update file(s) from wp-cli/.github

Fix import URL rewrite test using assume-https flag

Add .gitattributes file

See wp-cli/wp-cli#5070

Merge pull request #99 from wp-cli/regenerate-readme

Merge pull request #91 from wp-cli/fix-gherkin-issues

Fix Gherkin lint issues

Merge pull request #88 from wp-cli/no-lock-file

Merge pull request #84 from wp-cli/fix/wpcs-3.0-issues

Document use of the `IMPORT_DEBUG` constant (#82)

Add `composer phpcbf` (#80)