Assignment

Build a Rails API that accepts input which is a N x M matrix containing only 1 & 0 as elements, return a sub-matrix of maximum size with all 1s. 
For example, consider the below matrix. 
matrix =  [
           [1, 0, 1, 1],
           [0, 1, 0, 1],
           [1, 1, 1, 0],
           [1, 1, 1, 1]
          ]
The submatix with only 1's & maximum size is 
[
 [1,1,1],
 [1,1,1]
]

Expectations:
 - Ensure that there is code documentation, test cases
 - Please deploy the API on Heruko & share the endpoint
 - Share the github repository URL