support branches for vendor plugins
move rails_log_stdout to heroku org and use legacy branch
Bundler 1.2.0.pre
use bundler for ruby version
fix support for ENV['RUBY_VERSION']
warn when using the old ENV['RUBY_VERSION']
handle no ruby_version case
set old system path, since it gets overridden when user_env_compile is set
try --enable-load-relative for ruby 1.9.3
update ENV['RUBY_VERSION'] to match Bundler 1.2.0.pre dsl
refactor build_ruby? detection
use --enable-load-relative for mri
Revert "use --enable-load-relative for mri"

This reverts commit 2170532d5ff192982b9ea1f6c56498b89e090bfa.

--enable-load-relative is broken for 1.9.2
update changelog
run commands without stderr
avoid stderr when querying for ruby version

bundle commands can cause git errors:
fatal: Not a git repository (or any of the parent directories): .git

this commit avoids pulling this into ruby_version
ruby version copy change
update ruby versions copy / deprecation warning
update changelog
Reduce slug size

* Keep the gem cache (including Bundler's git cache) out of the slug.