update changelog
Update check_install with new install options
Fix default
Merge branch 'master' of github.com:conda/conda
Default the progress bar to stdout

Fixes #536
Merge branch 'master' into requests
Correctly handle 304 when fetching repodata
Correctly stream the pkg url so that the progress bar works
Let requests handle the retries
Use requests in download(), and use that in fetch_pkg()