chore(ci): drop testing for Ruby < 2.2

Author: DirtyF

.travis.yml

@@ -1,7 +1,5 @@
 language: ruby
 rvm:
-  - 2.0.0
-  - 2.1.10
   - 2.2.6
   - 2.3.3
   - 2.4.0
@@ -10,14 +8,10 @@ gemfile:
   - Gemfile
   - Gemfile-jruby
 
-matrix: 
+matrix:
   exclude:
     - rvm: jruby-9.1.9.0
       gemfile: Gemfile
-    - rvm: 2.0.0
-      gemfile: Gemfile-jruby
-    - rvm: 2.1.10
-      gemfile: Gemfile-jruby
     - rvm: 2.2.6
       gemfile: Gemfile-jruby
     - rvm: 2.3.3