v1.2.7

More updates to the default asset/Webpack/Mix configuration:

• Included a default mix-manifest.json so jigsaw build will work out of the box, without requiring an initial npm run dev
• Updated the default installation to include source/_assets and source/assets/build, along with a sample source/assets/build/css, source/assets/build/js, and source/assets/images directories.
• Set the processCssUrls option to false, to prevent Sass compilation from modifying URLs found in styles