Also pass browserify config on browserify init

Some options mentioned in [browserify-documentation] can only be set on
the init of browserify, not passed on the bundle method. Now both is
done…

[browserify-documentation]: https://github.com/substack/node-browserify/tree/4.2.3#var-b--browserifyfiles-or-opts
Also pass config to hashBundle init
Merge pull request #44 from alappe/browserify_config

Also pass browserify config on browserify init