adding test cases for integralByInterval() and integral()
adding test cases for integralByInterval() and integral()

bruce-lyft/graphite-web,g76r/graphite-web,g76r/graphite-web,g76r/graphite-web,bruce-lyft/graphite-web,g76r/graphite-web,bruce-lyft/graphite-web,bruce-lyft/graphite-web,g76r/graphite-web,bruce-lyft/graphite-web,g76r/graphite-web,bruce-lyft/graphite-web