Turn on coercion by default

[schwern]

#65 proposes adding a trait to turn on coercion. In Moose, coercion is declared on the type, but must be explicitly turned on at each use. Usually in an attribute, but also in signatures.

I find this very tedious. #66 will mitigate this somewhat by allowing one to make coercion the default. However I would rather it was the default as its conveniences outweigh its dangers. The Moose arguments against coercion seem to come from the C world where types don't make much sense and coercion is a far fuzzier concept.

My use cases are mostly about coercing strings into objects. URI strings into URI objects. File and directory paths into Path::Class objects. I'd rather if I'm using a type with coercion that it just worked without having to specially tell it to work.