REF: UserInfo may now be created from a session.
ENH: remove Session.user_info/AuthManager.user_info property.

They never really belonged there. We now can create a UserInfo instance
from a session instead when user info are really needed.
REF: remote setters, use a common update function for config.
STY+DOC: sort Configuration members, add docstring for every property.
MAINT: remove obsolete code.
REF: remove obsolete get_path, logic now in _from_legacy_locations.
Merge pull request #364 from enthought/remove_user_info_property

Remove user info property
BUG: fix warning message.
Merge branch 'master' into config_use_properties_and_update
DOC: fix docstrings.
ENH: make config.indices and config.indexed_repositories immutable.
ENH: make ProxyInfo 'immutable'.
Merge pull request #367 from enthought/config_use_properties_and_update

Config use properties and update
BUG: fix typo in -k flag handling + add test for it.
Merge pull request #368 from enthought/fix_insecure_handling

BUG: fix typo in -k flag handling + add test for it.
ENH: keep original exception when possible for auth failures.
BUG: handle fundamental settings when writing into a file.
Merge pull request #370 from enthought/fix_config_writing

Fix config writing
BUG: nicer error handling for SSL certificate errors.
BUG: fix python 3.