Update Circle CI to test on more Elixir host versions

Author: mobileoverlord

.circleci/config.yml

@@ -1,14 +1,97 @@
-# Elixir CircleCI 2.0 configuration file
-#
-# Check https://circleci.com/docs/2.0/language-elixir/ for more details
+install_elixir: &install_elixir
+  run:
+    name: Install Elixir
+    command: |
+      wget https://repo.hex.pm/builds/elixir/v$ELIXIR_VERSION.zip
+      unzip -d /usr/local/elixir v$ELIXIR_VERSION.zip
+      echo 'export PATH=/usr/local/elixir/bin:$PATH' >> $BASH_ENV
+
+install_hex_rebar: &install_hex_rebar
+  run:
+    name: Install hex and rebar
+    command: |
+      mix local.hex --force
+      mix local.rebar --force
+
+defaults: &defaults
+  working_directory: ~/repo
+
 version: 2
+
 jobs:
-  build:
+  build_elixir_1_8_otp_21:
     docker:
-      - image: circleci/elixir:1.6.6
-    working_directory: ~/repo
+      - image: erlang:21.2.7
+        environment:
+          ELIXIR_VERSION: 1.8.1-otp-21
+          LC_ALL: C.UTF-8
+          SUDO: true
+    <<: *defaults
     steps:
       - checkout
-      - run: mix local.hex --force && mix local.rebar --force
-      - run: mix deps.get --only test
+      - <<: *install_elixir
+      - <<: *install_hex_rebar
+      - run: mix deps.get
+      - run: mix format --check-formatted
       - run: mix test
+      - run: mix docs
+
+  build_elixir_1_7_otp_21:
+    docker:
+      - image: erlang:21.2.7
+        environment:
+          ELIXIR_VERSION: 1.7.4-otp-21
+          LC_ALL: C.UTF-8
+          SUDO: true
+    <<: *defaults
+    steps:
+      - checkout
+      - <<: *install_elixir
+      - <<: *install_hex_rebar
+      - run: mix deps.get
+      - run: mix format --check-formatted
+      - run: mix test
+      - run: mix docs
+
+  build_elixir_1_6_otp_21:
+    docker:
+      - image: erlang:21.2.7
+        environment:
+          ELIXIR_VERSION: 1.6.6-otp-21
+          LC_ALL: C.UTF-8
+          SUDO: true
+    <<: *defaults
+    steps:
+      - checkout
+      - <<: *install_elixir
+      - <<: *install_hex_rebar
+      - run: mix deps.get
+      - run: mix test
+
+  build_elixir_1_6_otp_20:
+    docker:
+      - image: erlang:20.3.8
+        environment:
+          ELIXIR_VERSION: 1.6.6
+          LC_ALL: C.UTF-8
+          SUDO: true
+    <<: *defaults
+    steps:
+      - checkout
+      - <<: *install_elixir
+      - <<: *install_hex_rebar
+      - run: mix deps.get
+      - run: mix test
+
+workflows:
+  version: 2
+  build_test:
+    jobs:
+      - build_elixir_1_8_otp_21:
+          context: org-global
+      - build_elixir_1_7_otp_21:
+          context: org-global
+      - build_elixir_1_6_otp_21:
+          context: org-global
+      - build_elixir_1_6_otp_20:
+          context: org-global