Fix SparseLinear

Fixed an issue with SparseLinear and added a test along with a new class
SparseJacobian (for testing sparse modules)
Merge remote-tracking branch 'upstream/master'

Conflicts:
	extra/nn/test/test.lua
Merge remote-tracking branch 'upstream/master'
Add extra tests for SparseLinear and fix bug where scale was not being multiplied into bias updates
Added one more test for SparseLinear
Merge pull request #189 from paidi/master

Fix SparseLinear