Adds a rate limiter for webs service requests
Merge branch 'master' into features/214-ratelimit-apikey

Conflicts:
	ichnaea/service/base.py
added a connection pool and pushed redis connection and pool into the config registry
pushed the redid configuration into the [ichnaea] config section
Merge remote-tracking branch 'crankycoder/features/214-ratelimit-apikey'
Move redis_con to a top-level cache module.
Only pass redis_con to the rate_limit function
Make it possible to override the test redis db and use db 1 instead of 0.

Using db 1 should minimize the risk of interfering with the default db.