#### 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
if (config.responseType === 'stream') {
        response.data = stream;
        settle(resolve, reject, response);
      } else {
        var responseBuffer = [];
        stream.on('data', function handleStreamData(chunk) {
          responseBuffer.push(chunk);
          
          if (config.maxContentLength > -1 && Buffer.concat(responseBuffer).length > config.maxContentLength) {
            reject(createError('maxContentLength size of ' + config.maxContentLength + ' exceeded',
              config, null, lastRequest));
          }
        });
        stream.on('error', function handleStreamError(err) {
          if (aborted) return;
          reject(enhanceError(err, config, null, lastRequest));
        });
        stream.on('end', function handleStreamEnd() {
          var responseData = Buffer.concat(responseBuffer);
          if (config.responseType !== 'arraybuffer') {
            responseData = responseData.toString('utf8');
          }
          response.data = responseData;
          settle(resolve, reject, response);
        });
      }
    });
    
    req.on('error', function handleRequestError(err) {
      if (aborted) return;