prevent buffer-browserify from getting included to reduce bundle size

[max-mapper]

this uses the Base64 module which is a smaller implementation than the previously used buffer-browserify one

it also upgrades concat-stream which now uses bops.is to check for bufferness instead of the previous Buffer.isBuffer which caused buffer-browserify to get included

before:

browserify index.js | wc -c
   86428

after:

browserify index.js | wc -c
   45525

[Raynos]

:+1: