please ignore this format for now - still not sure what's the optimal error message...
@myronmarston @JonRowe any suggestions?

I was thinking about something like:
```
Failure/Error: expect(invalid_collection).to all( eq('A') )
       expected ["A", "B", "A", "C", "A"] to all eq "A"
       
       object at index "1" failed: 
       expected: "A"
            got: "B"
       
       (compared using ==)
       
       
       object at index "3" failed: 
       expected: "A"
            got: "C"
       
       (compared using ==)
```