fix tmpdir for JRuby build task
clear cache for ruby 1.9.3 due to security upgrade
update changelog
clear cache on ruby_version change
cache_store can store files as well
chomp newline off of `ruby -v` output
load_bundle_cache -> load_bundler_cache
update copy
don't clear cache on new apps
update changelog
Revert "cache_store can store files as well"

This reverts commit 4bfc6dcab6ecf3c015b7b0eab402a7c3a7adef93.

This would lead to successive slug size increases, storing the vendor
directory into the vendor/bundle directory each time. Like:

vendor/bundle/bundle/bundle/....
use `vendor/heroku` for storing metadata b/t builds
cleanup mess from v37
always write ruby_version to the cache
can't cache_load a file
reinstall language pack gems since they live in `vendor/bundle`
update changelog
don't clear cache on new apps
actually purge the cache again on ruby version change
always need to reinstall language gems when clearing the bundler cache