Move creation of attributes to RequestException

Pass request objects in HTTPAdapter
Avoid having to fix tests
Explicitly check for None
Document requirements for SNI support on Python2

A section for Request's advanced usage guide on what Server Name
Indication is, its purpose, and how to enable it on Python2.
Move SNI documentation to FAQ

Relocate documentation on Server-Name-Indication from the advanced
section to the frequently asked questions. This is minus details on
enabling SNI on Python2, which is instead captured by linking to Stack
Overflow.
Reinstate falling back to self.text for JSON responses

A JSON response that has no encoding specified will be decoded with a detected UTF codec (compliant with the JSON RFC), but if that fails, we guessed wrong and need to fall back to charade character detection (via `self.text`). Kenneth removed this functionality (by accident?) in 1451ba0c6d395c41f86da35036fa361c3a41bc90, this reinstates it again and adds a log warning.

Fixes #1674
Remove logging and charade mention.

Logging is Not Allowed, so out it goes.
One last Charade reference to remove here.
Remove unused loggers.
Merge pull request #1901 from mjpieters/chardet-not-charade

One last Charade reference to remove here.
State early in SNI discussion Python2 limitation

Reference at the earliest opportunity that Server-Name-Indication is a
limitation of Python 2.6 and 2.7. Avoid describing it as a Requests
issue.
Document the `Response.reason` attribute.

Made `.status_code` and `.reason` consistent with one another, adding some examples. Addresses #1225.
Merge pull request #1904 from mjpieters/doc-response-reason

Document the `Response.reason` attribute.
Merge pull request #1902 from mjpieters/master

Remove unused loggers.
Clarify our 1.2.1 behaviour change.
Merge pull request #1900 from mjpieters/issue1674-json-fallback-encoding

Reinstate falling back to self.text for JSON responses
Merge pull request #1897 from aliles/master

Document requirements for SNI support on Python2
Merge pull request #1891 from sigmavirus24/add-requests-to-exceptions

Add request to RequestException
New Response property, .is_redirect.
Merge pull request #1918 from zackw/response-is-redirect

New Response property, .is_redirect.