100: Clean CSS - option to disable or set default options

[evanmwillhite]

Addresses https://github.com/fourkitchens/emulsify-gulp/issues/100

Description: Add the ability to disable CleanCSS entirely or reset some options.

To Test:

• Use your preferred method for testing a node module locally (e.g., npm link, setting this branch as your Emulsify package dependency, etc.) to install this branch of Emulsify Gulp in a new or existing Emulsify installation
• Use a local config or test by editing the default config to disable CleanCSS
• Run yarn start or npm start in your Emulsify instance and verify dist/style.css is not minified
• Test other options as needed

[evanmwillhite]

Awesome, thanks for reviewing @willthemoor!