Exonum 0.9.0 release (exonum#803)

Update Exonum version

Move testkit-server into a separate crate (exonum#718)

Update exonum version (0.7.0 -> 0.7.1)

Update exonum version (0.6.0 -> 0.6.1)

Release 0.7.0 (exonum#605) [ECR-1073]

Release 0.7.0 [ECR-1073]

Release 0.6.0 (exonum#533)

Update crate version

Merge pull request exonum#437 from DarkEld3r/release-0-5-0

Update version and reorganize changelog

Merge pull request exonum#391 from defuz/release-0.4

Bump version to 0.4 and clarify changelog