Trivially replace specs in test deps, imports with specs2.
Replace internal unfiltered.spec references with unfiltered.specs2.
Replace internal sbt unfiltered-spec references with specs2.
Add Specification to Hosted specs super stack.
Fix a few internal unfiltered-specs2 references.
Replace org.specs.Specification imports.
More missing Specification mixins.
Actual specs2 API changes.  library tests pass.
Remove shareVariables() calls; it's gone from specs2.
One more beSomething.
netty-server tests compile.
mac tests pass.
Mix in fail/skip support for those tests that use it.
netty-websockets tests pass.
oauth tests pass.
directives tests pass.
netty-uploads tests compile.
netty tests compile.
filter tests pass.
filter-uploads tests pass.  Under 2.10.3, all but netty{,-server,-uploads} subprojects tests pass, just like old specs.