Play 3.0 support

[tardigradeus]

ReactiveMongo Version

1.1.0-RC12

MongoDB version (2.6, 3.0 / etc)

Not important

Operating System (Ubuntu 15.10 / MacOS 10.10 / Windows 10)

Not important

JDK (Oracle 1.8.0_72, OpenJDK 1.8.x, Azul Zing)

Not important

Library Dependencies

Play framework 3.0.2

Expected Behavior

1. There is a release for Play 3.0

Actual Behavior

1. There is no release for Play 3.0

I'll create a PR with the modifications to support Pekko.