Merge branch 'feature/issue-5-sessions-until-state-metric' into feature/issue-6-time-between-states-metric
Separated metadata operations into separate functions
Created _set_metadata function
Added time_between_states metric
Added tests for time_between_states metric
Merge branch 'develop' into feature/issue-6-time-between-states-metric

Conflicts:
	lib/metrics-helper.js
Code cleanup
Renamed _get_metadata to _reset_metadata
Handled case where metadata doesn't exist in _reset_metadata
Merge branch 'feature/issue-6-time-between-states-metric' into develop