Adding circleci integration

Author: Yucong Sun

.circleci/config.yml

@@ -0,0 +1,23 @@
+version: 2.0
+
+jobs:
+  build:
+    docker:
+      - image: circleci/rust:stretch
+    steps:
+      - checkout
+      - run:
+          name: Setup
+          command: |
+            apt update -y
+            apt install -y cmake build-essential
+      - run:
+          name: Build libra-dev
+          working_directory: libra-dev
+          command: |
+            cargo build
+      - run:
+          name: Build everything else
+          command: |
+            mkdir build
+            cd build