Export PIP_DOWNLOAD_CACHE

switching curl from using -O option to -o because it is a little safer.

It is usually safer to use the -o option in curl to specifiy your own temp file name in scripts because if the file changes in the url then your local file will also change and it will result in an error since you have that name hard coded in the next few lines (tar, rm)

changing mkdir .heroku to mkdir -p .heroku since it is a little safer and won't throw error if directory already exists.

added a -p option to mkdir .heroku it is safer incase .heroku is already created, it won't error out

This reverts commit 30d04b17.

Django app Procfile generation broken

Change to fix an issue when DATABASES isn't declared in settings.py