Fix Hatetepe adapter and spec, broken by 69be64b and 17a9819
Merge pull request #168 from seancribbs/rspec3

Fix RSpec 3 compatibility (partially)
Don't define module_functions for HeaderNegotiation

Makes render_error() consistent with other places which
call the ensure_* helpers.
Shrink Trace::FSM's surface

Relieve Decision::FSM from the knowledge of Trace::FSM's API,
and shrink the surface to only #tracing_enabled?.