function _checkPath (npmPath) {
  return new Promise((resolve, reject) => {
    if (npmPath) {
      fs.lstat(npmPath, (err, stats) => {
        if (err || !stats || (stats.isDirectory && !stats.isDirectory())) {
          reject(new Error(strings.givenPathNotValid(npmPath)))
        } else {
          resolve({
            path: npmPath,
            message: strings.givenPathValid(npmPath)
          })
        }
      })
    } else {
      reject(new Error('Called _checkPath() with insufficient parameters'))
    }
  })
}
Attempts to get npm's path by calling out to "npm config"

@param  {string} npmPath - Input path if given by user
@returns {Promise.<string>}