Fast route without trying converters

[smarie]

From #5

matching converters will be called even if received value is of a valid type, except if a specific option skip_matching_converters_if_valid=True is set

[smarie]

I am not totally convinced with this. There is already a workaround: to provide an "identity" converter first in the converters list, accepting the field type. Of course that's a bit cumbersome...