Create some Scala Magic in response to the new OptionalBinder.

[nbauernfeind]

This fixes #22.

In particular, I added all of the necessary scala magic to be able to ask for Option[T], Option[Provider[T]] and Option[javax.inject.Provider[T]] instead of the Guava Optional equivalents. This is solved similarly to how ScalaMultibinder is implemented. The readme is updated as well.

This pull request only shares a single commit from the other commit, specifically 2145abf (adding new injector extension methods).

[tsuckow]

I am making my way through this. I did notice that the OptionProviderSpec was missing a test for when the Optional is absent, I added it in my local copy.

I still need to sift through the Binder. I am on travel the next few days so whatever I don't finish tonight will have to wait till at least the weekend.

[tsuckow]

I am unfamiliar with the higherKinds flag. The library seems to compile fine without it, what is this needed for?

[nbauernfeind]

That was a refactoring miss in this changeset; I'll remove it and update. That should only be in package.scala now.

It's the thing that allows me to do this:

private[scalaguice] type HKClassTag[CC2[_]] = ClassTag[CC2[_]]

  private[scalaguice] class WrapHelper[WType[_] : HKClassTag] {
    def around[T](typ: TypeLiteral[T]): TypeLiteral[WType[T]] = {
      val wType = Types.newParameterizedType(implicitly[HKClassTag[WType]].runtimeClass, typ.getType)
      TypeLiteral.get(wType).asInstanceOf[TypeLiteral[WType[T]]]
    }
  }

 private[scalaguice] def wrap[WType[_] : HKClassTag] = new WrapHelper[WType]

Specifically you can make a Manifest that takes a type parameter. I use it here to create a nice type-safe utility to wrap some T inside of some container (like a Set) by calling wrap[Set].around(typeLiteralOfT).

[tsuckow]

One down.

[tsuckow]

I just noticed that there are no tests for None in ScalaOptionBinder. That could be improved in a separate commit.