mod. rename 'interval' parameter to 'slice'.  This parameter defines the size of time series request slices.
Merge branch 'master' of github.com:rfaulkner/E3_analysis
mod.  rename aggregators + fix condition on qualifying a time series request.
mod. redefine UserMetricPeriod classes.  There are only two types REGISTRATION & INPUT.  Default is REGISTRATION.  In the URL INPUT is specified now by "activity".
mod. Change default start & end timestamps in UserMetric class.
Merge branch 'working'