FEAT: look in sys.prefix first, then ~ for config from now on.

A default configuration is written only if no config is found anywhere,
and is always the one in ~.
Merge branch 'master' into sys_prefix_first

Conflicts:
	enstaller/tests/test_main.py
FEAT: use sys.real_prefix to look for config when under venv.
MAINT: add a flake8 entry to ignore vendorized packages/modules.
Merge pull request #394 from enthought/add_flake8_config

MAINT: add a flake8 entry to ignore vendorized packages/modules.
BUG: keep old config search order in _from_legacy_locations.
BUG: fix config tests.
STY: fix pep8 violations in config.
REF: move config templates in separate module + style cleanups.
Merge pull request #392 from enthought/sys_prefix_first

Sys prefix first
STY: fix pep8 violations.
Merge pull request #395 from enthought/fix_flake8

Fix flake8 violations
ENH: bundle six in egginst and use it for python2/3 renames.

We bundle it in egginst as it is needed in both enstaller and egginst,
and we can't depend on enstaller in egginst.
MAINT: fix travis-ci script.
MAINT: fix travis-ci script.
MAINT: fix travis-ci script.
STY: fix pep8 violations.
STY: skip typo in comment.

[skip ci]
Merge pull request #396 from enthought/use_six_for_compat

ENH: bundle six in egginst and use it for python2/3 renames.
REF: wrap auth tuple in a class.

We still support setting auth as a tuple in the high level API (e.g.
Session class) like requests does.

This is the first step toward support for API token authentication.