Adds Schemas

Adds base schema for following Stripe objects

• balance_transaction
• charge
• coupon
• customer
• dispute
• event
• file_upload
• invoice_item
• invoice
• order_return
• order
• payout
• plan
• product
• refund
• sku
• subscription

Adds Skip Mixin

Merge pull request #1 from airflow-plugins/stripe

update README

Initial Release

v0.0.1

first commit