Updated `enb-bem-docs` to `0.4.0`
Merge pull request #977 from bem/issues/976@v2

Updated `enb-bem-docs` to `0.4.0`
(radio|checkbox)_type_button: won't work in IE9 (close #975)
Merge pull request #978 from bem/issues/975@v2

(radio|checkbox)_type_button: won't work in IE9 (close #975)
fix type check
Do not lint *.docs and *.tmpl-specs
Porting changes from islands-components/spin2
Merge pull request #971 from incrop/incrop.spin-port

spin: Port changes from islands-components/spin2
popup: nested popup doesn't consider zIndexGroupLevel of parent popup
(closes #970)
addition zIndexGroupLevel instead of choosing max + added unit test
use undef as initial state of _parentPopup