Bump to async 3.0.1

• New upstream version
  • Add node-babel-plugin-add-module-exports as dependency
  • Bump Standards-Version to 4.2.1, no changes needed
  • Change Vcs-* urls to Salsa
  • Updated d/copyright, removed deps/nodeunit.js
  • Add lintian override source-is-missing for
    • support/jsdoc/theme/static/scripts/prettify/lang-css.js line length is 390 characters (>256)
    • support/jsdoc/theme/static/scripts/prettify/prettify.js line length is 563 characters (>512)
  • Bumb to debhelper 11