Upgrade to Ruby 2.1.4

TEST

Change version in Gemfile and .travis.yml to "2.1.4".

Using a "fuzzy matcher" like "2.1" in .travis.yml (see c807ef2c1e9f16f195b152f42f2bbc6cd7feddb6) does not work at the moment. Travis will use rvm with 2.1.3, and the build fails due to mismatch of version specified in Gemfile and actual Ruby version.