add npm-cache-dir@1.0.0
Factor out getCacheStat

This is one of the first steps to factor out the git part of
`cache.js` into a separate module which can be tested separately.
archiveGitRemote
cloneGitRemote
checkGitDir
use option-hash, fix missing rm
inject methods, remove gitDoneCb
add npm-cache-git@0.0.1
use npm-cache-git