code: function downloadBootstrapAssets(version, path) {
    console.log(chalk.blue((`Downloading Bootstrap assets to ${path}`)))
    version = semver.clean(version)
    const url = 'https://maxcdn.bootstrapcdn.com/bootstrap'
    var proms = [
      'fonts/glyphicons-halflings-regular.eot',
      'fonts/glyphicons-halflings-regular.woff',
      'fonts/glyphicons-halflings-regular.woff2',
      'fonts/glyphicons-halflings-regular.ttf',
      'fonts/glyphicons-halflings-regular.svg'
    ].map(f => {
      return download(`${url}/${version}/${f}`, `${path}/fonts`)
        .catch(e => {
          console.log(chalk.red(`Downloading ${version}/${f} failed.`))
          return Promise.resolve()
        })
    })
  
    proms = proms.concat([
        'js/bootstrap.js',
        'js/bootstrap.min.js'
      ].map(f => {
        return download(`${url}/${version}/${f}`, `${path}/js`)
          .catch(e => {
            console.log(chalk.red(`Downloading ${version}/${f} failed.`))
            return Promise.resolve()
          })
      })
    )
    return Promise.all(proms)
  }
docs: Downloads bootstrap js and font files by given version to destination path.
  @param  {String} version Semver
  @param  {String} path    Save destination
  @return {Promise}