added gitignore
matrix now has array of row headers instead of linking them to the root
test reporting of > 1 solution
data objects are constructed with row and column header objects, which
are in turn constructed with row and column numbers

partial solution vector is data objects in the rows that are part of
the solution
find and print all solutions
made the algorithm a class
simple statistics; new test files
added pentominoes stuff
ignore .pyc files