Expand user_variables into individual columns of the session meta data
Merge branch 'dataview'
The ip_id_num is now grouped by (experiment_id, session_id) before enumerating. This should help merging etc.
Added the ability to retain certain columns, such as ip start times, in the filtered data
Use ujson if possible
Merge pull request #7 from pedmiston/master

Improvements to InterestPeriodDefinition class