Stable vs candidate cookbooks

[dmakhno]

Every cookbook is published as stable.
It make more sense to publish it as stable only if it has passed tests.

Like:

publish "check-${GIT_REVISION}"
replace "check-${GIT_REVISION}"

check python test_runner.py

publish "stable-${GIT_REVISION}" #or stable-${TRAVIS_BUILD_NUMBER}"
replace "stable-${GIT_REVISION}" #or stable-${TRAVIS_BUILD_NUMBER}"
publish_github

it is easier to manage storage, and clean failed cookbooks.

For stable I also prefer to use Build Number, due to incremental nature and more human hash.