Release v0.15 (paritytech#248)

* Add 0.15.0 changelog section

* Update CHANGELOG.md format

* Bump versions

* Update CHANGELOG.md

* Specify explicit version for client

* Remove unused subxt dev dependency

* Upgrade deps

Release v0.12.0 (paritytech#157)

* Bump version, update changelog

* Bump proc-macro crate

* Bump client crate

Release v0.11.0 (paritytech#145)

* Bump versions

* Update changelog

* Update PR links

* Fix changelog linebreak

* Remove explicit wabt-sys dependency

* Update changelog

* Update parity-scale-codec version

Upgrade to substrate rc4 release (paritytech#131)

* Upgrade to substrate rc4 release

* Fix up test-node/service

* Fix up client node config

* Fix up remaining compilation errors

* Fmt

* Remove fixme

* Fix test

* Release v0.10.0

Release v0.9.0 (paritytech#129)

* Bump version, update changelog

* Add client version

Release v0.8.0 (paritytech#117)

* Bump version to 0.8

* Update changelog

v0.7.0 release extras (paritytech#110)

* Explicit proc-macro version for crates.io release

* Upgrade partity-scale-codec

* Add proc-macro crate metadata

Release v0.6.0 (paritytech#90)

* Update to substrate alpha 6

* Bump version and add release notes

* Upgrade async-std dev dependency

* Fix readme license links

Release v0.5.0 (paritytech#80)

* Update README.md

* Update to alpha.5 substrate packages

* Add identity storage hasher

* Bump version

* Add CHANGELOG.md

* Update crate metadata for publishing

* Update url crate