every engine and their version should write into peerDependencies

[denghongcai]

example package.json

{
  "dependencies": {
    "less": "2",
    "accord": "0.28.0"
  }
}

npm and npminstall now will not 100% obey directory structure, if dep is not within peerDependencies, it means accord may not get 2.7 version using require.resolve.