Rdio album and tracks w tests

parentheses are useful in regex for logical grouping (eg, "group this stuff together, and then apply some operator after it like `?` meaning "this may be present but maybe not" or `*` meaning "this group may appear any number of times"), but also mean "capture this stuff". later on, the first captured group gets assigned to `id`. if you don't want a parenthetical to be captured you can begin it with `?:`

for example:

```ruby
>> /hello (world)/.match("hello world")[1]
#=> "world"
>> /hello (?:world)/.match("hello world")[1]
#=> nil
```

if we don't need to capture an id for these, let's not capture an id