Separated generic functions from build helpers.
Changed:
- Moved 'utils/*.js' to 'helpers/*.js'
- From 'utils/config.js':
- Moved function `merge` to 'utils/index.js'.
- Moved function `isObjectLike` to 'utils/index.js'.
- From 'utils/template.js':
- Moved function `flatten` to 'utils/index.js'.
- Moved function `escapeRegExp` to 'utils/index.js'.
- From 'tasks/styles.js':
- Moved function `createPostCSSProcessor` to 'helpers/postcss.js' as `createProcessor`.
- Replaced function `Object.assign` with `merge` for task options parsing in all tasks.