Implement Min Heap

[saurabh47]

Implement MinHeap class that supports:

• building Min Heap from an input array of integers
• Removing the heap's minimum / root value
• Inserting integers in the heap.
• Peeking at heap's minimum / root value
• shifting integers up & down the heap, which is to be used when inserting & removing values.

[maheshj01]

heap implementation and related leetcode problems were solved in #37