Updates to modern gem structure

* Removes jeweler, re-scaffolded with bundler
* gemspec and version upgraded
* Started moving code inside of ActiveRecord
  We are limited by just how much we cando from outside of AR.
  By properly integrating into AR, we can inherit all its goodness
Works toward integration.

I got each_row working already. \o/
each_instance working again
Adds each_x_by_sql, Model.each_row features

* Removes in-line testing.
* Works for ActiveRecord (Rails) 4.1
* Still need to test AR 4.0
* Not planning on supporting AR 3.x anymore! Use gem v0.4.x
* Should be ready for use now, but more testing underway.
Updates README, removes unneeded files
Fixes for 4.0.x compatibility
Missed one 4.0 fix
Typos in constant names
Merge pull request #11 from gocardless/v0.5-rails-4.0-fixes

V0.5 rails 4.0 fixes
Use ActiveRecord version instead of Rails'

...So this will work in non-Rails apps
Adds test-app, removes unused ~/activerecord files
Tested against AR 4.1.2.rc1 and Edge (4.2.0?)
Adds support for Rails/ActiveRecord 3.2.x and up!

That wasn't too bad. Since 3.2 is still supported by Rails, we can too.
Tests are working again!

* Added "rake setup" task to create db/table
* "rake [test]" to run them
Enabled Enumerable for deferred row processing

README now markdown (yay!)

Smoothed out test app
Updates the lazy enumerable example
Adds pluck_rows and pluck_instances feature

This is a light-weight version of pluck.
Fixes gem version badge
the test-app is included in the console session
Cleaned up code