ci: add elixir 1.10 to travis.yml (#165)

Also: removed 1.5 build

.travis.yml

@@ -1,16 +1,16 @@
 language: elixir
 matrix:
   include:
-    - elixir: 1.5.3
-      otp_release: 20.3.1
-    - elixir: 1.6.6
-      otp_release: 20.1
-    - elixir: 1.7.3
-      otp_release: 21.0.9
-    - elixir: 1.8.2
-      otp_release: 21.0.9
-    - elixir: 1.9.1
-      otp_release: 21.0.9
+    - elixir: 1.6
+      otp_release: 21.0
+    - elixir: 1.7
+      otp_release: 22.0
+    - elixir: 1.8
+      otp_release: 22.0
+    - elixir: 1.9
+      otp_release: 22.0
+    - elixir: 1.10
+      otp_release: 22.0
 before_install:
 - openssl aes-256-cbc -K $encrypted_3033c569c247_key -iv $encrypted_3033c569c247_iv -in secrets.tar.enc -out secrets.tar -d
 - tar xvf secrets.tar

README.md

@@ -7,7 +7,6 @@
 [![Hex.pm](http://img.shields.io/hexpm/dt/pigeon.svg)](https://hex.pm/packages/pigeon)
 
 ## Installation
-*Requires Elixir 1.4/OTP 19.2 or later.*
 
 Add pigeon and kadabra as `mix.exs` dependencies: