allow ability to read in env
make sure all rake tasks go through `RakeRunner`
set user env for bundle install and rake
add env var blacklist
use options hashes for RakeRunner
always use rake when running rake task
setup env vars properly for rails3/4 assets:precompile
switch for when user-hash present or not
default_database_url should not set the DATABASE_URL env var
fix shell helper bugs
use new env dir format
remove unnecessary parameter
rake assets:clean also needs env
need to setup bash shell env when passing env during run