Refactored library and radionet class

- Changes in radio.net API (added support for configurable apikey)
- Added better caching
- Added support for browsing additional categories

tests/conftest.py

@@ -0,0 +1,24 @@
+from unittest import mock
+
+import pytest
+
+from mopidy_radionet import backend
+from mopidy_radionet.radionet import RadioNetClient
+from mopidy_radionet.library import RadioNetLibraryProvider
+
+@pytest.fixture
+def backend_mock():
+    backend_mock = mock.Mock(spec=backend.RadioNetBackend)
+    backend_mock.radionet = RadioNetClient(proxy_config=None)
+    backend_mock.library = RadioNetLibraryProvider(backend=backend_mock)
+    backend_mock.radionet.set_apikey('test')
+    backend_mock.radionet.set_favorites({'lush'})
+    return backend_mock
+
+@pytest.fixture
+def library(backend_mock):
+    return backend_mock.library
+
+@pytest.fixture
+def radionet(backend_mock):
+    return backend_mock.radionet