Fix development dependency is preferred over dependency.

If a dependency occurs in both the `dependencies` and the `devDependencies`
sections of package.json, npm should prefer the version from the `dependencies`
section since it is what is used when installed with `--production`

A warning is issued with information about what version is used.

A brief discussion can be found in this comment.
https://github.com/npm/npm/issues/5403#issuecomment-45278489