ZeroMatrix.__nonzero__ returns False
Merge branch 'master' of github.com:sympy/sympy
Trace.doit() produces Sum
MatMul.doit supports deep
add trace function
trace doctest - add use_unicode=False
add matrix factorizations
Factorizations preserve real/complex element types
explicit import in test_factorizations
Trace.doit calls obligatory doit on Sum
Identity sympifys arg
Add trivial Matrix.doit()
Trace no longer evaluates.  trace evaluates.

Also, trace no longer rewrites as Sum
Trace._eval_rewrite_as_Sum
FunctionMatrix._eval_trace = Trace._eval_rewrite_as_Sum
trace docstrings
xfail Trace rewrite as Sum test
remove commented refine factorization tests
Merge pull request #2155 from mrocklin/matrix-factorizations

Add MatrixExpr Factorizations
Test and fix for Point.is_collinear coincident point error.

Previously, if the first two points passed to Point.is_collinear were
coincident, the method would always return True.  This is fixed by converting
the point list to a set to remove identical points.