cmdline honours csvDir parameter
Redis store
Redis store has connection parameters
Store type can be configured with flags or config
Config.go supports environment variables
Config allows double-binding when safe
It configures REDIS store with VCAP_SERVICES
Redis supports passwordless connections
fix travis
Workload Steps have an optional context parameter

Fixes the previously non-concurrency safe way of sharing state between
workload steps. Now a workload step can specifically ask for a context
map which is created before and passed between each workload step.
Rest workloads use context
Tidy up