Close #469 Add GStreamer state tests

Add 3 test cases to test GStreamer states: record, pause, and stop

test_current_state_is_record(): checks that the current state is RECORD
test_current_state_is_pause(): checks that the current state is PAUSED
test_current_state_is_not_stop(): sets state to null, then checks that
current state is not STOP

Related #437
Remove framework/rss_parser.py
added notification_manager file and modified record file
fixed some bugs, to do: add frontend functions
modified notification_manager, added frontend methods
modified add and delete methods on framework side
finished implementing add and remove functions (frontend)
modified frontend functions, added notification label list
Changing ScrollArea to QListWidget