Implemented Stringer on matrices
Tested/fixed string
Update Frustum test (0 < Near < Far invariant)
Fix missing negative sign in Frustum
Merge pull request #27 from go-gl/fix-frustum

Fix missing negative sign in Frustum
Fixed typo/bug in MulMxN
Added the matrix stack
Added test
Fixed rebase and added example
Added to mgl64
Fixed makefile and reran to update package for 64-bit
Rebase -> Reseed
Added a real rebase from an arbitrary location
Documentation update
Fixed comment in rebase example
Merge branch 'collision' of github.com:go-gl/mathgl into collision