add simpson files

[ariya122]

No description provided.

[hamidrezanorouzi]

I want simpson 1/3 and simpson 3/8 in form of functions.
For simpson 1/3 use "simpson13" as the name for the function and the file.
for simpson 3/8 use "simpson38 as the name for the function and the file.

write test codes to show how you can use these functions (simpson13 and simpson38) to integrate f(x).