Add billing data methods

Add a method to get current and past billing data.

Add new membership methods

Adds more methods to administrate users and memberships. See documentation about users and memberships for details.

Add optimize_source support for uploading images

Adds options to upload image to support optimize_source. See documentation about source images for details.

Fix sharing of config data between instances

Thanks to @raphaelsaunier for discovering an issue in #47.

JSON.stringify on metadata

Avoids request trying to read metadata as a Stream.
Fixes #45

Remove `module` entry from package.json

create-react-app have issues with the module entry:
https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/template/README.md#npm-run-build-fails-to-minify

So we removed it. Only publishing the lib/ as the main entrypoint.

1.0.0 - update deps & tooling

• Add module/main to package.json for better tooling information.
• adds browser usage info (fixes #41)
• updates version to 1.0.0 - it's about time
• uses newer versions everywhere
• ensures preset-env with a sensible default is used
• clarifies usage of babel-runtime (fixes #36)

0.28.1 - fix metadata upload in browser

• fixes an issue with adding metadata during upload when using it in the browser (#42)

0.28.0 - copy/restore, metadata on upload, babel-runtime improvements

• add copy and restore (#40)
• allow to add metadata on upload (#39)
• make sure babel-runtime is installed (#38)

0.27.0 - stack expressions

• Add support for stack expressions (#37)
• Add support for overwrite stack (#35)