add travis configuration

Author: valich

.travis.yml

@@ -0,0 +1,20 @@
+language: ruby
+dist: trusty
+os:
+  - linux
+  - osx
+
+rvm:
+  - 1.9.3
+  - 2.0.0
+  - 2.1.10
+  - 2.2.8
+  - 2.3.5
+  - 2.4.2
+  - 2.5.0-preview1
+  - ruby-head
+
+matrix:
+  fast_finish: true
+  allow_failures:
+    - rvm: ruby-head