function parseDependencies (pkgJson, fields) {
	// bundleDependencies and bundledDependencies are optional. we need to
	// exclude those form the final [name, version] pairs that we're
	// generating.
	const bundleDependencies = parseBundleDependencies(pkgJson)
	const allDependencies = mergeDependencies(pkgJson, fields)
	const names = Object.keys(allDependencies)
	const results = []
	for (let i = 0; i < names.length; i++) {
		const name = names[i]
		if (bundleDependencies.indexOf(name) === -1) {
			results.push([name, allDependencies[name]])
		}
	}
	return results
}
extract specified dependencies from a specific `package.json`.
@param  {Object} pkgJson - plain JavaScript object representing a
`package.json` file.
@param  {Array.<String>} fields - array of dependency fields to be followed.
@return {Array} - array of dependency pairs.