Add missing tests for other types of bolus

There was no test for dual wave or square wave bolus.
This adds a fixture to test them.
Make basal record validation more accurate

0 rate basal records are perfectly valid.
If the rate is missing altogether, it's invalid.
Merge pull request #10 from tidepool-org/bewest/basal-cleanup

Make basal record validation more accurate
Merge pull request #11 from tidepool-org/bewest/bolus-fixtures

Add missing tests for other types of bolus