Update ruby version in travis.yml

Nokogiri requires ruby >= 2.1.0 to be used, and fails to complete travis build

Author: guiscaranse

.travis.yml

@@ -5,7 +5,7 @@ script: "./script/cibuild"
 #environment
 language: ruby
 rvm:
-  - 2.0.0
+  - 2.1.0
 
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