consolidate run commands
allow ability to read in env
make sure all rake tasks go through `RakeRunner`
use options hashes for RakeRunner
always use rake when running rake task
pass user env when detecting rake tasks
set user env for bundle install, rake, rails3/4 assets:precompile
add env var blacklist
use new build env arg format using a directory of env vars
need to setup bash shell env when passing env during run
Merge pull request #201 from heroku/uec_spike

buildpack-env-args...ponies!
heroku hatchet 1.1.9
Merge pull request #215 from heroku/schneems/update-hatchet

heroku hatchet 1.1.9
Fix parallel bundler tests

- Always use a tmpdir to download bundler.
- Remove un-used methods `Ruby.bundle` and `Ruby.bundler_path`.
- Re-name `install_language_pack_gems` to `install_bundler_in_app` since that's all it ever does
- Copy bundler into app path instead of re-downloading
Merge pull request #212 from heroku/schneems/parallel-bundle-wrapper-fix

Fix parallel bundler tests
update changelog
bump to v93
Cleanup language pack config var setup, especially with PATH
always return @slug_vendor_base in slug_vendor_base
add quiet option for RakeTask#invoke