fix(directives): fixed error handling in directives registry
test(directive): Added a test for DirectiveRegistry
fix(parser_generator): fixed class selector
fix(ng_repeat): Gracefully handle non-lists
test(ng_repeat): Test for gracefully handling nulls
chore(directive_spec): Remove an iit
hack(directives): Work around dartbug.com/13556
docs(ng-if): added docs

See issue #126
chore(ng-if): some cleanup

See issue #126
test(ng-if): add more tests

See issue #126