lib/plugins/plugin/install/install.js/PluginInstall/installPeerDependencies
class PluginInstall:  installPeerDependencies() {
    const pluginPackageJsonFilePath = path.join(
      this.serverless.config.servicePath,
      'node_modules',
      this.options.pluginName,
      'package.json'
    );
    return fse.readJsonAsync(pluginPackageJsonFilePath).then(pluginPackageJson => {
      if (pluginPackageJson.peerDependencies) {
        const pluginsArray = [];
        _.forEach(pluginPackageJson.peerDependencies, (v, k) => {
          pluginsArray.push(`${k}@"${v}"`);
        });
        return BbPromise.map(pluginsArray, this.npmInstall);
      }
      return BbPromise.resolve();
    });
  }