Fix array_equal and array_equiv issue

array_equal() and array_equiv() don't work for string arrays and record arrays. This is because those methods use numpy.equals ufunc for comparison, and there are no equal ufuncs registered for strings and record arrays. Replace numpy.equals with '==' array operation, which handles strings and record arrays.
Make sure comparison result is array
Merge pull request #3322 from ContinuumIO/array_equal_fix

Fix array_equal and array_equiv issue