Change Path type in IAM resources to be Token[String]

[jfklingler]

Fixes #148

This may warrant a minor version bump. The implicit conversion from String to Token[String] should take care of InstanceProfile. Since there's also an implicit conversion from T to Option[T], if people did not explicitly specify the Path in ManagedPolicy as Some("blah"), compilation will fail since only one implicit conversion will be applied.

[bkrodgers]

I guess we could add an implicit conversion for Option[String] to Option[Token[String]] to make that backwards compatible. Thoughts?

[jfklingler]

I don't think that will help. If Path = "blah", we'd need an T => Option[Token[T]] implicit conversion. I can try that, but there are already quite a few implicit conversions floating around. I suppose we could make a more specific String => Option[Token[String]] IC, but that seems like overkill in the name of backward compatibility for a relatively simple and probably obvious change.

[bkrodgers]

Since it was already an Option[String], hopefully most people were specifying it as Some("string") already. In that case, the current implicits should pick it up, right? It's only if they were relying on the implicit from String -> Option[String] that it'd break?

[jfklingler]

That's correct.