Merge branch 'psr-15'

Merge pull request #17 from php-middleware/psr-15

psr-15

Update README.md

Merge pull request #13 from php-middleware/feature/config-provider

Config provider for zend expressive

Merge pull request #12 from php-middleware/bugfix-slim3_compatibility

Slim3 compatibility

Merge pull request #7 from php-middleware/docs

Update docs

Merge pull request #1 from weierophinney/hotfix/seek-to-eof-before-write

Fix issue with rewound response bodies

Update README.md