Add `.hweights' method & `wnorm.2d.ssa'
Add `wnorm.2d.ssa' example
Add `wcor.2d.ssa'
Add examples and test for `wcor.2d.ssa'
Add `wcor.2d.ssa' test
Remove remaining semicolons
Merge pull request #44 from eodus/wX4

W-cor matrix for 2D-SSA