CI: Migrate to circle CI 2.0

[TomAugspurger]

1.0 is being shut down: https://circleci.com/blog/sunsetting-1-0/?mkt_tok=eyJpIjoiT0dFMVkyWXlZV05pT1RFNSIsInQiOiJrWVJVc0lUSjZ3NSttZHJDM2h2UFhoY0JacGw4YUNwR09qb1QwZzRFM2NOKzk4WEI5VXhxS055S2JPbVdFUWdmbWVPWmx5R0N1TFB6ZEFsZm5JUklob1dXTXAzZWtCaWpYSmE0TUdSd3RRemh3WWYxMDhleHhtVkh0dU9obStGRiJ9

• http://go.circleci.com/E020Z0bCMOi0k0MH2Z04G00
• http://go.circleci.com/p0400Z00DH0M0PkM2G0biZ2
• http://go.circleci.com/r40Q0H2Z0MEGikZ0b00M020

[tnir]

@TomAugspurger Any update? 2.5 months left.

[jreback]

a pull request to change this would be helpful

[jreback]

adding to the dev sprint

we have to switch this by august!