Class Informer isn't needed in IDA 7 since IDA can identify vtables for you (assuming you have the pro version).
As for signatures, I recommend you use a script to generate the sig for you. SM has a good one called
makesig.idc. However, if you're using that script with IDA 7 you'll need to run a find+replace on it to replace all instances of "dtype" to "dtype" for it to work.