Updates and moar security

• Use roave/security-advisories package to prevent installing packages with known vulnerabilities
• Add WP_CACHE_KEY_SALT constant to allow object cache isolation
• Update rarst/laps package to next major version (2.0)
• Update all packages, sync composer.lock
• Micro-optimisation: replace dirname( __FILE__ ) with __DIR__
• Remove unnecessary parentheses from language constructs (require, require_once)
• Update README

1.0.0, codename "Sonata No. 1 in F Major"

This is the first, non-WIP, ready-to-use version of the project.

• added WP-CLI support
• added support for .env files via vlucas/phpdotenv
• added .env.example
• added post create-project command to copy .env.example to .env and generate WordPress salts with WP-CLI
• added keywords and support (issues) link to package metadata
• added requirement for PHP 7.0 and up
• added requirement for native gettext PHP extension
• added Level 2/A: Authoritative class maps autoload optimization to composer.json
• added post create-project command to symlink current default WordPress theme (Twenty Seventeen)
• removed redundant version from package metadata
• updated README

You can listen to Beethoven's Sonata No. 1, used as a codename for this version, here.

0.1.0

• added a complete set of rules to .gitignore
• started tracking composer.lock
• added this CHANGELOG
• replaced .gitkeep files with WP's empty index.php
• updated README