formatInline does not catch IllegalArgumentExceptions

[dhoepelman]

We've been using this library in combination with require to constrain our domain objects, but still get nice JsErrors back.

Unfortunately this does not work with Jsonx.formatInline

case class PositiveInteger(i: Int) {
   require(i >= 1, "Number must be a positive integer")
}

import play.api.libs.json.Json
// JsError(ValidationError("Number must be a positive integer"))
Jsonx.formatCaseClass[PositiveInteger].reads(Json.parse("""{ "i": -1 }""")))

// IllegalArgumentException("Number must be a positive integer") gets thrown
Jsonx.formatInline[PositiveInteger].reads(Json.parse("-1")))

I might be able to create a PR for this friday if this is wanted