trial_1

tried importing the BSM model which sindhu made
31_Jul_integrated_non_unif_grids

1) change the method of calculating the deltas from last to an average
of bid and ask. Most of the last values are remaining the same for the
underlying.
2) incorporate the file into sindhu's main file.
Revert "trial_1"

This reverts commit d3ec8ed0c39ac8557e0ba49517503ff4aceefff1.