Cache gets bloated by old package versions

[ryphill]

The buildpack does not clean up older versions of the packages it installs which leads to the dyno size becoming bloated over time.

Lets say that you have the package example installed and between every deploy you do a new version of it gets released by the upstream. After 5 deploys, you will have 6 versions of the package in your cache the current version and the 5 previous ones.

If you have a handful of large packages installed then you'll eventually run close to or over heroku's soft size limit of 300MB.