Add backwards compatibility for filter_parameters in Rails3

Commit e93132c added support for Rails 4, but it broke the automatic
filter_parameters in Rails 3. This adds backwards compatibility for
Rails 3.
fix middleware for AC::Metal on rails 3.2

Fixes #248
Add tasks specific for using appraisal to test different versions
of Rails as well as Rack, Rake & Sinatra to Rakefile
Update CircleCI to use parallelization to run tests for all integrations and cucumber tests for all environments
explicitly
Ensure that integration tests can use the same helpers as unit tests
Fix errors causing features to fail
Add sqlite3 for Rails 3.2 & 4.0 appraisal gems
Fix integrations with Rails 3.0 by locking sucker_punch to v1.0.2.
ActionDispatch::Reloader causes errors when hit in the sucker_punch v1.0.3 library.
Update README.md

Fix CircleCI badge
Add tests, minor refactor for Rails 3 functionality
added airbrakeman notifier ruby illustration
illustration added, take 2
Merge pull request #285 from airbrake/adjust-ci-integration

Adjust ci integration

@zefer reviewed
Merge pull request #281 from jhawthorn/fix_actioncontroller_metal

fix middleware for AC::Metal on rails 3.2
Added Airbrakeman Notifier Illustration
Only send notices if configured with api_key

Currently if the gem is included, but not configured, it will intercept
exceptions and attempt to send them to api.airbrake.io without an
api_key.

This changes the behaviour of send_notice to only send a notice if
airbrake is configured.  This defines configured mean it has a non-blank
api_key.
Merge pull request #268 from alphagov/disable_unless_configured

Only send notices if configured with an api_key
Merge pull request #287 from itolmach/master

Added Airbrakeman Notifier Illustration
Add support for regexp filters
Refactor cgi_data filtering to use `filter_key?`
Add a default rack env filter for variables matching "secret" or "password".