Simplify travis.yml

Author: lowks

.travis.yml

@@ -1,17 +1,12 @@
-language: erlang
+language: elixir
+elixir:
+  - 0.14.3
+  - 0.15.0
+  - 0.15.1
+  - 1.0.0
 otp_release:
   - 17.0
   - 17.1
 env:
-  - ELIXIR="v0.14.3"
-  - ELIXIR="v0.15.0"
-  - ELIXIR="v0.15.1"
-  - ELIXIR="v1.0.0"
+  - MIX_ENV=test
 install: mix deps.get
-before_install:
-  - mkdir -p vendor/elixir
-  - wget -q https://github.com/elixir-lang/elixir/releases/download/$ELIXIR/Precompiled.zip && unzip -qq Precompiled.zip -d vendor/elixir
-  - export PATH="$PATH:$PWD/vendor/elixir/bin"
-  - export MIX_ENV=test
-  - mix local.hex --force
-script: mix test