Lazy application of functions

This redesigns Mul to be a more general Applied, that is, Mul(A,B) becomes applied(*, A, B).

Fast sum, fix getindex for Mul

v0.5.2

Test #22

v0.5.1

Fix #12 by supporting mixed shapes

Add MulArray/InvArray, Add, and better support for multiple argument Mul

v0.5.0

avoid recursive calls to Mul

Improve Ldiv, Inv, and PInv

v0.4.0

test pinv/inv

Improve Vcat addition

v0.3.2

smarter 2 term vcat

Fix dimension checking in Mul

v0.3.1

Increase coverage

Redesign MulAdd

v0.3.0

default to MulPlus, remove blas macros

Reduce compile time

v0.2.1

reduce compile time, restore general Mul getindex

Add Kron and support for lazy triangular matrices

v0.2.0

test sizes in copyto! for Kron