React to Options changes

FYI the file is spelled wrong: SignalRServiceColletion
Thanks. I learned about service replacement last night after I sent the previous comment (we haven't yet done the work on either EF or Identity to enable that). That narrows it down to just #1 or #2. 

One thing I don't like about #2 is that adding the Configure method to the SignalR services builder (hint: if SignalRServiceCollection isn't an IServiceCollection maybe it should be called SignalRServiceBuilder :smile:, similar to what we do in EF and Identity) is that users could chain multiple calls to it and have the expectation that the actions will be executed in the same order in which the calls appear on the chain, but we currently don't have a mechanism to do that. 

For that reason I am going to suggest that we stay with #1 and that we remove the Configure method, at least for now.