Converting to RSpec and Rails3

Major overhaul of the development side of this gem. Please don't
hesitate to let me know if you run into any issues.
moving test_lib into spec/support
version: 3.0
fixing manifest
fixing version reference
so much easier to read
gemspec fixes
removing the log that snuck in
allowing @record.destroy(validate: false) to skip validations
version bump
ignoring ./pkg
allowing extending the window
version bump to 3.0.3
Test in several versions of ActiveRecord

Note that tests fail in AR 3.2.12
Make "spec" the default rake task

Travis uses the default task to try to run tests
Change to public run_callbacks API
Fix environment variable communication
Protect against empty env variable
Use travis to run build matrix
Remove check for 1.8.7, it is not compatible