100 narray exercises

This is narray version of 100 numpy exercises

1. Import the narray gem

   require "numo/narray"

2. Create a null vector of size 10

   p Numo::Int32.zeros(10)
   p Numo::Float32.zeros(10)

3. Create a null vector of size 10 but the fifth value which is 1

   Z = Numo::Int32.zeros(10)
   Z[4] = 1
   p Z

4. Create a vector with values ranging from 10 to 49

   Z = Numo::Int32[10..49]
   p Z

5. Reverse a vector (first element becomes last)

   Z = Numo::Int32[0..49]
   p Z.reverse

6. Create a 3x3 matrix with values ranging from 0 to 8

   Z = Numo::Int32[0..8].reshape(3,3)
   p Z

7. Find indices of non-zero elements from [1,2,0,0,4,0]

8. Create a 3x3 identity matrix