Start testing against Elixir 1.10 (elixirs#322)

* Start testing against Elixir 1.10

* Travis doesn't support 22.2.5 yet so using 22.2.4

* Quote elixir versrion so Travis doesn't try to download 1.1

Author: anthonator

.travis.yml

@@ -16,20 +16,20 @@ jobs:
     - script: mix credo --strict
       name: "Credo"
       stage: lint
-      elixir: 1.9
-      otp_release: '22.0.7'
+      elixir: '1.10'
+      otp_release: '22.2.4'
     - script: mix format --check-formatted
       name: "Formatter"
       stage: lint
-      elixir: 1.9
-      otp_release: '22.0.7'
+      elixir: '1.10'
+      otp_release: '22.2.4'
     - script: mix dialyzer --halt-exit-status
       name: "Dialyzer"
       stage: typecheck
       env:
         - MIX_ENV=dev
-      elixir: 1.9
-      otp_release: '22.0.7'
+      elixir: '1.10'
+      otp_release: '22.2.4'
     - elixir: '1.5'
       otp_release: '20.3.8.22'
       script: mix test
@@ -50,6 +50,10 @@ jobs:
       otp_release: '22.0.7'
       script: mix test
       stage: test
+    - elixir: '1.10'
+      otp_release: '22.2.4'
+      script: mix test
+      stage: test
 
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