Make json test-data easier to read

Also allow test-data to be regenerated more easily with
env variable REGENERATE_TEST_DATA
Allow source and destination to be scalars or objects
Start TestHelper module to build test dags
Fix: to_hashref should sort edges list
Merge branch 'master' of github.com:genome/ptero-perl-sdk
Update DAG-JSON.t to use TestHelper
Update DAG-Validation.t to use TestHelper
Fix orphaned nodes validation on DAG
Merge pull request #14 from davidlmorton/master

Start on TestHelper
Add Graph dependency to cpanfile
Add cycle-detection to DAG validation
Add another cycle-detection test
Merge pull request #15 from davidlmorton/master

Cycle Detection