New test for non-existing id
refactored persistence.getById to use array.filter instead of iteration
Added or corrected global directive
Merge pull request #20 from leider/master

Habe Gregors Vorschlag umgesetzt
Made persistence tests order independent
Merge branch 'persistence-improvement'

Conflicts:
	test/persistence_test.js
Merge pull request #21 from ggramlich/master

Some improvements on the persistence
fixed typo
ignore persisted json files for grunt watch task
persistence.save method is now async
Merge pull request #22 from ggramlich/master

persistence.save method now has an async interface
merged with master