RC Travis test speed up ideas

.travis.yml

cache: 
   - db/max_fixture_date
   - db/max_script_date
   - db/test_data_cache.sql
script: bundle exec rake db:test:from_travis_cache test

0_README.md

@jcalvert I wanted to confer with you on how this might help speed up our RC test suite on travis: https://github.com/ridecharge/rc/blob/master/lib/tasks/refresh_data.rake#L29-L64

I'm thinking of saving the data locally right before each test run.

refresh_data.rake

# lib/tasks/refresh_data.rake
namespace :db do
   namespace :test do
       task :from_travis_cache => ['db:load_from_cache', 'db:quick_refresh', 'db:migrate', 'db:cache_data']
    end
    task :load_from_cache do
       `touch db/test_data_cache.sql;
         mysql rc_test < db/test_data_cache.sql`
    end
    task :cache_data do
       `mysqldump rc_test > db/test_data_cache_new.sql`
       `if [[ “$(md5 -q db/test_data_cache_new.sql)” -ne “$(md5 -q db/test_data_cache.sql)” ]]; then 
          mv db/test_data_cache_new.sql db/test_data_cache.sql;
         fi`
    end
end