Update Travis config.

Test Ruby 2.0 and 2.2; remove 1.9.3.

This should fix the build and shouldn't matter since 1.9.3 is very old.

.travis.yml

@@ -8,13 +8,20 @@ git:
 node_js:
   - "0.12"
 
+env:
+  matrix:
+    - RUBY_VERSION=2.0
+    - RUBY_VERSION=2.2
+
 before_install:
-  - rvm use 1.9.3
+  - rvm install $RUBY_VERSION
+  - rvm use $RUBY_VERSION --fuzzy
+  - export GEMDIR=$(rvm gemdir)
 
 install:
   - travis_retry npm install -g grunt-cli
   - travis_retry npm install
-  - travis_retry gem install --no-document "jekyll:~>2.5.3" "rouge:~>1.8" "sass:~>3.4"
+  - travis_retry gem install --no-document "jekyll:~>2.5.3" "rouge:~>1.9" "sass:~>3.4"
 
 matrix:
   fast_finish: true