RMSProp implementation modeled off of AdaDelta
Add running averages as members of RMSProp class

This enables us to use them as monitored values.
Reorder things in SGD.setup, so we call learning_rule.get_updates
before learning_rule.add_monitoring_channels.
Also add a little bit of doc.
Docs, error/exception updates, and addition of SGD._setup_monitor
Learning rule doc fix + PEP8 for learning_rule tests
Merge pull request #1026 from madisonmay/master

RMSProp learning rule implementation