Faster compile time

[sboerrigter]

Fixes #794.

Changed

I've changed the following, based on issue #794:

• Remove the lint police (especially SCSS, we know best practices by now)
• Prefix less browsers (see: Autoprefixer: support less browsers #784)
• Remove welcome message, colors dependency
• When dropping all linters, README can be heavily simplified (see: Move information from Wiki to Readme #797)

Not changed

I did not yet look into the following points, but I created new issues for them so we can close #794 and merge this PR before we release 1.9.0.

• Drop Fancybox as a default dependency so the base64 task can be removed (see: Replace Fancybox with Photoswipe #416)
• Run development builds unless specified. Minification, for example, is not necessary during development (see: 768)
• Remove globbing (:trollface:) (wontfix)
• Switch to Rollup/Webpack/Broccoli if compilation speed differs much from Gulp (see: Replace Gulp with Webpack/Rollup/Broccoli #818)

[luukdv]

• I see you've removed the composer.json file. Why? Right now, the Sphynx\Installer doesn't work anymore and I'm pretty sure composer create-project trendwerk/sphynx stopped working.
• I see you've upgraded the dependencies, can you do this with PHP too? 5.4 → 5.6
• Did you test the upgraded dependencies like webpack-stream? gulp can't be started anymore (error), when downgrading it works again.

[sboerrigter]

I just re-added composer.json. I thought this was only used for PHPCS 🙃.

PHP has been upgraded to 5.6.

I reverted the update commit so Webpack works again.