[#45119889] Cross publish Newman using Scala 2.9.1, 2.9.2, and 2.10.0.

* Looks like the implicit resolution rules changed in 2.10.0. The previous way the implicits were defined it was only working for this.URLCapable, this.Builder, etc.
* The organization of the DSL's may need to be reviewed based on the 2.10.0 implications. The URLBuilderDSL is organized differently than the others now (outside of the DSL trait). /cc @arschles
* Had to bump specs2 to 1.12.3 which seems to be the minimal working version with Scala 2.10.0.