Add -C flag that enables caching, but flushes the cache beforehand.
Merge pull request #5 from heroku/clear-cache-flag

Add -C flag that enables caching, but flushes the cache beforehand.
add magic curl support for curl with non-zero exit codes
Deprecated warning
Deprecated warning
Merge branch 'master' of https://github.com/heroku/heroku-buildpack-testrunner