Remove name argument from Discovery classes

[sagikazarmark]

As discussed in #4

Reason against it: it allows to identify a class resource and allows to override it when registering one.

/cc @ddeboer

[ddeboer]

I prefer to remove the names and use priorities to make overriding lookups possible. Perhaps manually register()ed classes should always go before the default ones? That’s probably sufficient.

[sagikazarmark]

Priority only make sense when you register your custom adapters. I guess you won't install more than one adapters. Even if you would, you shouldn't care about which exactly is instantiated.

If this is true, we should just unshift the manually registered classes => done.

[ddeboer]

True, just put manually registered classes on top (so unshift).