Expose raw validation results

[dnd]

As per @apotonick's request in #410 here is a PR to start the conversation about changes to Reform.

A couple things I noticed as I went through this.

• #failure? did not actually return a boolean value. It just returned whatever was in @failure. Since a new #failure method was being added, I updated #failure? to be more consistent with the expectation of a ? method.
• Is the result.rb line 9 is correct behavior? Should it instead be a map? As it is now, it's just going to find the first failure of the combined lists. Couldn't there be multiple?

[dnd]

@apotonick I don't think these failures are the fault of anything I did, are they?

[emaglio]

@fran-worley @apotonick should we consider these changes for the next release - if yes, let’s add it in the 2.3v milestone