move marcxml fixtures to fixtures/ subdirectory
move ```test/handle```, update ```validate-aco-marcxml_test.rb```

Move ```test/handle``` to fixtures directory ```test/fixtures/handle```.
Update ```validate-aco-marcxml_test.rb``` to use ```#teardown``` to reset
  unreadable file permissions.
move ```test/wip``` to ```test/fixtures/wip```
Merge pull request #21 from NYULibraries/add-fixtures-subdirectory

Add test/fixtures/ subdirectory