Add get_logout_headers to request

The documentation for forget() says it is deprecated and to use get_logout_headers() on the request instead.  However, no such method has been added to the request.
Remove reference to request.get_logout_headers()
Merge pull request #1250 from dobesv/patch-2

Add get_logout_headers to request
improve timeout docs
79-char line widths!
reproduce timeout=None bug
fix timeout=None bug as well as some other potential unpacking problems
reproduce reissue_time=None bug
handle reissue_time=None properly
Merge branch 'fix.1247'
update changelog
Hand RepozeWho1AuthenticationPolicy.remember kwargs to repoze.who #1249

Documentation for pyramid.security.remember supports keyword arguments
to hand over to the authentication policy. However, when using
RepozeWho1AuthenticationPolicy, all of the kw were dropped in remember.

It is my understanding that with repoze.who, additional configuration
parameters shall be stored in the identity dictionary. In our case,
setting the max_age parameter to the authtkt identifier, would be done
using an identity {'repoze.who.userid':principal, 'max_age': 23}.

It seems sensible just to hand over kw through the identity dictionary
and all users to specify max_age or other parameters such as userdata.
Merge pull request #1254 from rbu/repozewho1-remember-kwargs

Hand RepozeWho1AuthenticationPolicy.remember kwargs to repoze.who (master) #1249
update inconsistent effective_principals docs

fixes #1196
'request_method' is *not* limited to the named set.
Minor punctuation and grammar changes to Quick Intro
Merge pull request #1263 from slinkp/slinkp_quickintro_doc_fixes

Minor punctuation and grammar changes to Quick Intro