adding default overrideable AWS region

Allows fog connections to non US-EAST regions of AWS by
allowing this property to be overriden in stub files (meta.fog_config.region).
Bump src/gorouter

Bump :
  Bruno Alvisio and Zach Robinson:
     Ensure custom stale threshold cannot exceed default stale threshold.
     Route endpoints can now request their own staleness threshold.
Merge remote-tracking branch 'origin/pr/551' into develop