Add API call for pairwise distance computation

[ayan-b]

Related to #51.

A new API for this:

Let's say that I have 180 points. On the first iteration I take the first one and compute the distance to the other 179, on the following iteration i take the second one and compute the distance to the next 178, and so on.

In particular, for n points we would consider the 1st one as source and rest of the (n - 1) ones as target and, then 2nd one as source and (n - 2) as target and so on...