feat: introduce data fetching via Relay / GraphQL

[jednano]

fix #13

Features

• Data fetching via Relay / GraphQL
• Automatic code generation via relay-compiler + graphql-codegen
  • Codegen plucks GraphQL queries from components that use babel-plugin-relay via babel-plugin-macros.

Related Issue

#13

Motivation and Context

Better performance by telling a component exactly what data it will need; thus, preventing over-fetching or under-fetching.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality
  to change)

Checklist:

• I have signed the
  Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.