added diagonal dominance functions, update src

yep:
- added ```isRowDD```, ```isColumnDD```, ```isStrictlyRowDD```, ```isStrictlyColumnDD```; these functions are useful for numerical stability-related junk.
- wrote appropriate tests
- made ```matrix.zeros``` better (realized I originally use ```Array.push()``` instead of allocating the right amount of memory using ```new Array(n)```
- updated src/ (the new implementation of the "naive" prime function was not updated in the source)

cc @LarryBattle