clean database before FactoryGirl.lint

We were experiencing intermittent FactoryGirl.lint failures which appeared to
have been caused by the database not being fully cleaned between test suite
executions.

Moved database clean operation before FactoryGirl.lint and followed ThoughtBot
recommendation to wrap FactoryGirl.lint in a begin/ensure/end block.

References:
https://github.com/thoughtbot/factory_girl/blob/master/GETTING_STARTED.md
http://devblog.avdi.org/2012/08/31/configuring-database_cleaner-with-rails-rspec-capybara-and-selenium/
Merge pull request #55 from NYULibraries/tweak-fg-lint

Clean database before FactoryGirl.lint
update database.yml for Jenkins local database

Add Jenkins-specific environment variables to config/database.yml so
that Jenkins can execute the test suite using its own (local) MySQL
instance instead of relying on a remote MySQL database.
constrain JENKINS_DB_* environment variables to test:
Merge pull request #56 from NYULibraries/update-database-config

update database.yml for Jenkins local database
Merge pull request #57 from NYULibraries/development

bring master branch up to speed with development branch