Update devDependencies

[josephpage]

• MAJOR : chai-spies@0.7.0 - Release Notes
• MAJOR - dox@0.8.0 - Release Notes (npm run docs still generates good docs with success)
• minor - mysql@2.8.0 - Release Notes
• update changelog.md

Generating docs :

> docker-compose run sequelize npm run docs
npm info it worked if it ends with ok
npm info using npm@2.7.5
npm info using node@v1.6.4
npm info predocs sequelize@3.5.1
npm info docs sequelize@3.5.1

> sequelize@3.5.1 docs /sequelize
> node docs/docs-generator.js

/sequelize/docs/api/hooks.md
/sequelize/docs/api/errors.md
/sequelize/docs/api/sequelize.md
/sequelize/docs/api/model.md
/sequelize/docs/api/instance.md
/sequelize/docs/api/associations/belongs-to.md
/sequelize/docs/api/associations/index.md
/sequelize/docs/api/associations/belongs-to-many.md
/sequelize/docs/api/transaction.md
/sequelize/docs/api/deferrable.md
/sequelize/docs/api/datatypes.md
/sequelize/docs/api/associations/has-many.md
/sequelize/docs/api/associations/has-one.md
npm info postdocs sequelize@3.5.1
npm info ok 

[janmeier]

Did you test whether all the docs are still generated correctly with the new version of docs (npm run docs)

[josephpage]

Hey @janmeier . Tests are all OK !!! 😎 👊
And yep, npm run docs still generates correctly docs.

[janmeier]

Thanks @josephpage ! :)