Bump Elixir version

.travis.yml

@@ -1,10 +1,8 @@
 language: elixir
 sudo: false
 elixir:
-  - 1.6
   - 1.8
 otp_release:
-  - 20.3
   - 21.1
 notifications:
   recipients:
@@ -25,10 +23,10 @@ jobs:
       script:
         mix format --check-formatted
         mix credo
-      elixir: 1.6
+      elixir: 1.8
     - stage: types
       env:
         - MIX_ENV=dev
       before_script: travis_wait 20 mix dialyzer --plt
       script: mix dialyzer --halt-exit-status
-      elixir: 1.6
+      elixir: 1.8

mix.exs

@@ -5,7 +5,7 @@ defmodule Hunter.Mixfile do
     [
       app: :hunter,
       version: "0.5.1-dev",
-      elixir: "~> 1.6",
+      elixir: "~> 1.8",
       docs: docs(),
       package: package(),
       source_url: "https://github.com/milmazz/hunter",