Make data optional on SquareMatrix construction
Ensure that fill also prevents non-square data
Merge pull request #71 from KartikTalwar/abstract-structures

Cofactor calculator for square matrices Rel: #59
Cofactor cleanup
Added Euclidean distance calculation to vector.
Oops, forgot to add vector.js. Recommitting.
Merge pull request #79 from revivek/abstract-structures

Added Euclidean distance calculation to vectors