Update date in changelog (php-http#166)

* Update date in changelog

* minor

* minor

* minor cleanup

Prepare for 1.9.1 (php-http#170)

* Prepare for 1.9.1

* Added more indentation

Merge pull request php-http#147 from php-http/patch-changelog

Added changelog for 1.9.0

Use deferred to be full async in retry (php-http#101)

Use deferred to be full async in retry

Merge pull request php-http#93 from php-http/changelog

Prepare for 1.7