There's composer error while running composer install on php 5.6.

Your requirements could not be resolved to an installable set of packages.

Problem 1

• Installation request for ocramius/package-versions 1.1.2 -> satisfiable by ocramius/package-versions[1.1.2].
• ocramius/package-versions 1.1.2 requires php ~7.0 -> your PHP version (5.6.30) does not satisfy that requirement.
  Problem 2
• Installation request for ocramius/proxy-manager 2.0.4 -> satisfiable by ocramius/proxy-manager[2.0.4].
• ocramius/proxy-manager 2.0.4 requires php 7.0.0 - 7.0.5 || ^7.0.7 -> your PHP version (5.6.30) does not satisfy that requirement.
  Problem 3
• Installation request for twig/twig v2.3.2 -> satisfiable by twig/twig[v2.3.2].
• twig/twig v2.3.2 requires php ^7.0 -> your PHP version (5.6.30) does not satisfy that requirement.
  Problem 4
• twig/twig v2.3.2 requires php ^7.0 -> your PHP version (5.6.30) does not satisfy that requirement.
• twig/extensions v1.4.1 requires twig/twig ~1.20|~2.0 -> satisfiable by twig/twig[v2.3.2].
• Installation request for twig/extensions v1.4.1 -> satisfiable by twig/extensions[v1.4.1].

Steps to reproduce:
1. Get fresh version of repo (I checked 1.7, 1.8, 1.9 and 2.0 branches. Bug occures on each of them)
2. Run composer install