message: Update CHANGELOG for v1.3.0
diff: # Changelog
  ## vNEXT
  +## v1.3.0
  +#### :rocket: Feature
  +* `apollo-cli`, `apollo-codegen-core`
  + * [#480](https://github.com/apollographql/apollo-cli/pull/480) Initial support for client-side schemas ([@shadaj](https://github.com/shadaj))
  +
  +#### :house: Internal
  +* `apollo-cli`, `apollo-codegen-core`, `apollo-codegen-flow-legacy`, `apollo-codegen-flow`, `apollo-codegen-scala`, `apollo-codegen-swift`, `apollo-codegen-typescript-legacy`, `apollo-codegen-typescript`
  + * [#479](https://github.com/apollographql/apollo-cli/pull/479) Run `build` before publishing to prevent uploading stale code ([@shadaj](https://github.com/shadaj))
  +
  +#### Committers: 1
  +- Shadaj Laddad ([@shadaj](https://github.com/shadaj))
  +
  ## v1.2.0
  #### :rocket: Feature
  * `apollo-cli`
  