Migrate to CircleCI v2 (#1517)

Use the new Docker-based, beta version of CircleCI.

This adds a docker image that has the correct deps to run flow, and then migrates from the old circle.yml format to the new.

This gets test runs wayyyyy down. Earlier today, on the old stack, before optimizations, we were at > 9 min for PR builds (aka, CI runs without a website deploy). The build for this PR ran in 1 min 33 seconds. Woo!

scripts/build-push-docker.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+
+set -eo pipefail
+
+docker build -t reactcommunity/node-ci:7.10.0 -f ./ci.Dockerfile .
+docker push reactcommunity/node-ci:7.10.0

scripts/ci.Dockerfile

@@ -0,0 +1,6 @@
+FROM node:7.10.0
+
+RUN apt-get update -y && \
+    apt-get install -y ocaml libelf1 && \
+    rm -rf /var/lib/apt/lists/* && \
+    curl -o- -L https://yarnpkg.com/install.sh | bash

scripts/test.sh

@@ -3,7 +3,7 @@
 set -eo pipefail
 
 case $CIRCLE_NODE_INDEX in 
-  0) yarn test ;; 
+  0) yarn test && yarn codecov ;; 
   1) cd examples/NavigationPlayground && yarn test ;; 
   2) cd examples/ReduxExample && yarn test ;; 
 esac