MAINT: Fix failures/warnings in test_api_shim.py

- Fixes a warning on indexing with a float that ultimately came from
  pd.Timedelta.total_seconds().  Adds ``timedelta_to_integral_seconds``
  and ``timedelta_to_integral_minutes()`` functions and replaces various
  usages of ``int(delta.total_seconds())`` with them.

- Fixes a warnings triggered in ``_create_daily_stats`` from
  passing tz-aware datetimes to np.datetime64.

zipline/utils/numpy_utils.py

@@ -18,6 +18,7 @@ from numpy import (
     flatnonzero,
     hstack,
     nan,
+    timedelta64,
     vectorize,
     where
 )