using datetime instead of date
history views can take a 'since' parameter
added a management command to generate test metrics
added a todo list
added methods to categorize metrics
update docs and fix tests for R._date_range
fix date creation in tests
moved tests into a package
fixing tests for metric history view
fix tests for aggregate history view
full coverage for R class
started tests for utils module
tests for utils.get_r
added tests for utils.metric
test for utils.gauge
test for utils._dates
tests for utils.generate_test_metrics
100% test coverage
added MetricCategoryForm; started tests for forms
complete tests for TestAggregateMetricForm