add Ruby 2.1 to Travis and update Rails versions for Appraisal
replace Appraisal with multiple Gemfiles like sprockets-rails
fix gemspec path for Rails 4
tweaking Travis Gemfiles
update bundler for Travis tests

as recommended: https://twitter.com/roidrage/status/419207786346848256
ignoring this error on JRuby and Rails 3.2

ActiveRecord::JDBCError: The driver encountered an unknown error: org.postgresql.util.PSQLException: FATAL: database "recurring_select_test" does not exist
Merge pull request #42 from GetJobber/testing

add Ruby 2.1 to Travis and update Rails versions for Appraisal