Improve Test Coverage

[Zazama]

• Removes unreachable ID3 Tag header validity check in the remove API, because an ID3 Tag is only found when its header is valid
• Add tests for NodeID3.removeTags
• Add tests for all NodeID3.update API branches
  • Reorder types to allow for calling NodeID3.update(tags, filepath, callback) (without options)
• Add tests for frame builder throws
• Add tests for tags whose data can be changed in frame builder (e.g. undefined => empty string)
• Add tests for update compare key

Coverage went from 77.66% to 87.71%