Better support for Collections of Primitives

[tabdulradi]

Due to limitation of Java generics, there is no Codec[int], only Codec[java.lang.Integer].
But also Datastax's driver won't let you define one from Scala (raises exception at Constructor).

Since, Scala compiler won't pick an implicit of M[java.lang.Integer] as M[Int]. This affected Troy implicit Codecs feature. As a solution, a hack was introduced for List and Set, to have a wrapper TroyCodec, that maps on every item on the collection to convert it from the Java Wrapper to the Scala Primitive.

But for Map, and Tuples, this hack would require order of magnitude more boilerplate. So currently they only support Wrapper classes, like Map[Integer, String]

See #8 and https://github.com/tabdulradi/troy/pull/17/files