Revert "Removed Jeweler from project"

This reverts commit 9ee3220271f4da408a51b33e3f915a46c5b26c1a.
Removed lockfiles
Updated .gitignore
Fixed test deprecations
Modified travis config: removed 1.9.2 and added 2.1.0
Add some travis sugar
Temporarily removed some build targets for faster test runs
Test gemfile update
Possible fix for ActiveRecord 2.3
Require activesupport for supporting MRI 2.0.0 and up
Remove old tasks and messages from Rakefile
Optional requirement for iconv for Ruby 2.0 and up
Regenerated gemspec
Test against new activerecord gemfile
Test against ActiveRecord versions 2.3-4.0
Test with development dependencies
Disable fast finish
Finalise new appraisals and gemfiles
Add development gems to Gemfile
Send test coverage data to coveralls