Make sure the contact retrieved is owned by current_user

Previous query returned a random contact record that may or may not have been
owned by current_user, causing the test to fail.
Change model from CronTrigger to Account

test_datetime_miliseconds assumed that a CronTrigger existed that had been
fired, which may not be the case for all SalesForce orgs (new org,
development org, etc)
Revert to testing CronTrigger in test_datetime_miliseconds

Test will be skipped if there are no CronTrigger records retrieved from SalesForce.
Merge pull request #29 from jacobwegner/fix-test-failures

Fix test failures where assumed data does not exist