Added ability to specify multiple backend server connections, and changed all caching to use redis instead of redis + database

* monitor_addr is now deprecated, instead use monitor_addrs as in example
* the Blob table is no longer used for anything. It will be removed in the future. All cached values that were stored there are now in the cache proper
* Tasks run periodically to cache all currently online workers for all servers, instead of doing so on a per-address basis
* Scheduled tasks have been split into cache related tasks and db-changing related tasks, allowing a passive version of celery to run for staging
* Workers now display their stratum connection address when connected
Adds forgotten example of how to set stage variable
Adds a cache refresh function.
Fixes #16 -- timeouts are now correct for all caching items
Changed schedule for setting average difficulty
WIP for worker stats temps+hashrate graphs
WIP for worker stats temps+hashrate graphs
WIP. Functionality for worker stats pretty much completed, needs a lot of cleaning up
Fixes a bug with tabs
Abstracts JS click grabbing function for worker stats/user stats
imports cleanup
minor fix to user stats
Fix user stats graph bug introduced by worker stats
Several minor cleanups, changes Nan = NaN in user_stats, etc
Completed cleanup function that actually works now. Adds new key that defines the N margin for cleanup
Patch an uncaught divide by zero error
fix pool graph links
stats pt 2 news update