ENH: workaround some buggy firewall stripping 'Content-Encoding' from http headers.

This was detected on at least one customer's private network, caused by "McAfee Web
Gateway" product.
BUG+REF: fix circular imports issues.
DOC: remove dev guide.

It was getting redundant with our examples.
DOC: add API doc for session.
DOC: fix intro + class links in examples.
ENH: emulate requests when our custom decompression fails.
Merge branch 'master' into workaround_buggy_firewalls_v2

Conflicts:
	enstaller/cli/tests/test_utils.py
Merge pull request #357 from enthought/workaround_buggy_firewalls_v2

ENH: workaround some buggy firewall stripping 'Content-Encoding' from ht...
FEAT: add verify and max_retries support in config.
ENH: config's max_retries and ssl_verify are now handled by enpkg.
Merge pull request #362 from enthought/move_verify_max_retries_in_config

Move verify max retries in config
MAINT: add 4.7.6 entry in bootstrap.
Merge pull request #366 from enthought/update_bootstrap_entry

MAINT: add 4.7.6 entry in bootstrap.
DOC: fix intra-references for classes in examples.
FEAT: add a download method for simple, reliable downloads.
DOC: update example to use session.download instead of session.fetch.
Merge pull request #361 from enthought/tweak_doc

Tweak doc