Deis Slugbuilder v2.4.9

v2.4.8 -> v2.4.9

Features

• 30d2caa Makefile: set docker build flags via environment variable

Fixes

• 6d0d344 download_buildpack: define name of buildpack

Maintenance

• 7638ca7 buildpacks: update heroku-buildpack-nodejs to v93
• ac0192f buildpacks: update heroku-buildpack-ruby to v150
• 3f4ccc4 buildpacks: update heroku-buildpack-python to v97
• c40c6a0 buildpacks: update heroku-buildpack-php to v117