Prepare for 1.7.0 (#64)

Merge pull request #46 from php-http/Nyhom-changelog

Added changelog

Merge pull request #39 from Nyholm/patch-changelog

Added change log

Prepare for 1.3 (#32)

* Prepare for 1.3

* Update CHANGELOG.md

* Update CHANGELOG.md

Prepare release

Added support for cache validation with ETag and Last-Modified headers.

Minor fixes

Initial release