Add support for Scala 2.11

[edrevo]

Hello,

I am using this library in one of my projects (great library, btw. thanks for open sourcing it!) but I am using Play 2.6 on Scala 2.11. Would you accept a PR to enable cross-compilation in SBT for scala 2.11 and 2.12?

[edgarmueller]

Hi,
yes, sure thing.