Add pkgin installer.#218

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weakish wants to merge 4 commits intosprinkle-tool:masterfrom

Commits on Jul 10, 2016

Commits on Jul 11, 2016

pkgin: refator to use `auto_api`.
weakish
committed

Commits on Jul 14, 2016

has_pkgin(): use `grep -E` instead of `egrep`.
weakish
committed