Switched to list when when creating Supernova object.
Modified order of instruction in distance matrix block to get more speed (not too much).
Using Python lists in creation of Supernova object, gives 2.37 speed up (speed up 137%(?!))
Implemented list-based version of get_distance method. Removed Masked arrays. Code 952 times faster.
Added ability to calculate isolated blocks of distance matrix.
Fixed bugs in new implementation of get_distance.
Modified indexing ability to calculate isolated blocks of distance matrix: included offset on j index.