Make sure composer/vendor does not clash

[cliffordp]

Investigate if multiple plugins including the same package from Composer causes any issues. If yes, consider these:

• https://github.com/TypistTech/imposter-plugin --> https://typist.tech/portfolio-item/imposter/
• https://deliciousbrains.com/php-scoper-namespace-composer-depencies/ --> https://github.com/humbug/php-scoper
• https://github.com/coenjacobs/mozart