A package that contains checks that npm runs during the installation.
.checkEngine(target, npmVer, nodeVer, force, strict, cb)
Check if node/npm version is supported by the package. If not
strict and it isn't supported,
cb is called with the error
object as its second argument.
.checkPlatform(target, force, cb)
Check if OS/Arch is supported by the package.
.checkCycle(target, ancestors, cb)
Check for cyclic dependencies.
Check if a folder is a .git folder.