get_bulk_archive now uses python tempfile and unlinks immediately to avoid using an explicit temp directory
removed reference to config.TEMP_DIR in test.py
removed references to TEMP_DIR from setup_ubuntu.sh
test_bulk_download now tests that the response data is a valid zip file
changed tempfile.mkstemp() call to tempfile.NamedTemporaryFile(delete=False)
Merge branch 'flask-rewrite' of https://github.com/jacksingleton/securedrop into jacksingleton

Conflicts:
	install_files/source.config.py
	securedrop/test.py
	setup_ubuntu.sh

This merge rebases on top of master. It also fixes the use of
NamedTemporaryFile, making it so deletion is handled automatically by the
class, and adding a prefix to the temporary filenames to make debugging easier.
Removed all references to TEMP_DIR throughout the codebase.