Vendor requests v2.0.0
Use requests instead of urllib2
Remove threaded page downloads

Threaded page downloads was causing issues with the requests
pool being closed. It also makes this area of code harder to debug
and quite often the pool has a size of 1.

Further more the pool only affects the scaning of the index which
should not have as great of a need for parallezation now that there
is only a single request per download by default.
Ensure that we successfully utilize requests timeout functionality
Pass our created session into RequirementSet
Enable Basic Auth either inside of urls or by prompting
Update requests test for the new funcargs
Catch the requests SSLError instead of ssl.SSLError
Move the requests.HTTPError into it's own exception handler
Add a missing text from the exception message
Refactor error hnadling into a function
Remove old error handling that is no longer required
Remove unused imports
Remove the now unused SSL backport code
Merge pull request #1145 from dstufft/use-requests

Use requests instead of urllib2