PreparedRequests don't carry proxy information.

The proxy info appears to be carried on the session. The only remnants
of proxy handling are this line in __init__().
Use full URL when contacting proxies.

Requests should use the full URL, not the path URL, when forwarding
traffic through proxies.
Remove unneeded import.
Merge pull request #1060 from Lukasa/proxy

Provide full URL to proxies.
Make sure proxies have their scheme attached.
Remove silly print statement.
Merge pull request #1071 from Lukasa/master

Proxies should have schemes.
Remove safe_mode/danger_mode from docs
Merge pull request #1076 from sigmavirus24/master

Remove (safe|danger)_mode references from docs
Update LICENSE
Fix #1079

Restore the functionality from here:
https://github.com/kennethreitz/requests/blob/v0.14.2/requests/models.py#L884
Update the advanced doc to use the r.json method
Update the link headers doc to match the code
Clarify support for alternative distributions
Merge pull request #1089 from PaulMcMillan/philosophy

Clarify support for alternative distributions
Merge pull request #1086 from graingert/patch-2

Update the link headers doc to match the code
Merge pull request #1085 from graingert/patch-1

Update the advanced doc to use the r.json method
Merge pull request #1080 from sigmavirus24/master

Fix #1079
Allow for third argument in file dict value to support explicit
file content type.
Fixing test to ensure it passes with python 3.