#### Summary

It looks like latest version includes `buffer.js` on the browser bundle even if not actually used.
This makes axios bundle size **3 times bigger**, adding 22kB to the minified size (0.16.0 is 11.9 KB while 0.16.1 is 33.9kB).

#### Context

- axios version: v0.16.1

lib/adapters/http.js
var parsed = url.parse(config.url);
    var protocol = parsed.protocol || 'http:';
    if (!auth && parsed.auth) {
      var urlAuth = parsed.auth.split(':');
      var urlUsername = urlAuth[0] || '';
      var urlPassword = urlAuth[1] || '';
      auth = urlUsername + ':' + urlPassword;
    }
    if (auth) {
      delete headers.Authorization;
    }
    var isHttps = protocol === 'https:';
    var agent = isHttps ? config.httpsAgent : config.httpAgent;
    var options = {
      hostname: parsed.hostname,
      port: parsed.port,
      path: buildURL(parsed.path, config.params, config.paramsSerializer).replace(/^\?/, ''),
      method: config.method,
      headers: headers,
      agent: agent,
      auth: auth
    };
    var proxy = config.proxy;
    if (!proxy) {
      var proxyEnv = protocol.slice(0, -1) + '_proxy';
      var proxyUrl = process.env[proxyEnv] || process.env[proxyEnv.toUpperCase()];
      if (proxyUrl) {
        var parsedProxyUrl = url.parse(proxyUrl);
        proxy = {
          host: parsedProxyUrl.hostname,