initial value for cumulative integration

When I use culum_integrate, it appears that it integrates 1 index beyond the array.

```
using NumericalIntegration
a = LinRange(0,1,100)
print(integrate(a,a), ' ')
print(last(cumul_integrate(a,a)))
```

returns:
```
0.5 0.5000510152025299
```

Is there a way to define the initial value of the integration so that it returns an integration for 0 to 1 with the first index being the initial value?