Upgraded to Gatsby v2

This is a Gatsby v2 compatible version of the lumen starter, started by the folks at Gatsby Central.

Here's a little recommended reading for Gatsby v2.

• First, what's new in v2
• Next, when should I upgrade?
• The Gatsby v2 announcement blog post

If you do decide to upgrade, these articles will help you do that.

• Getting started with Gatsby v2
• Should I rebuild my site for Gatsby v2?
• How do layouts work in Gatsby v2
• StaticQuery in Gatsby v2

Finally, here's a cheat sheet we prepared to help during the upgrade:

• Gatsby v2 refactoring cheat sheet