Removed some dependencies on the sublime Python API so Package Control works with the site also
Fixed a bug with fetching info about packages having more than one release
Changed the repository provider get_packages() method to be able to function as a generator
Added missing sys import for ca_certs.py
Refactored downloader, client and provider stack to use exceptions so we can capture and store errors for later reference
Changed the download manager to use a contextmanager to ensure the download managers are always released, even if an exception is raised