added unit test for operator_to_vector failure reported in #217
fixed bug in operator_to_vector / vector_to_operator
new fix for #237
Merge pull request #1 from qutip/master

Pull from upstream
First attempt at making super_tensor work for states. See #238.
Merge branch 'master' of github.com:cgranade/qutip

Conflicts:
	qutip/permute.py
	qutip/tensor.py
	qutip/tests/test_qobj.py
Forgot an import in new unit test.
Fixed bug in permute. Unit tests now pass locally.
Merge pull request #240 from jrjohansson/fix-issue-237

Fix issue #237
replace double .H with double .T as @cgranade suggested
Changed type == 'super' to issuper, etc.
Merge pull request #242 from jrjohansson/fix-issue-237

replace double .H with double .T as @cgranade suggested
Added composite() as discussed in #241.
Merge pull request #241 from cgranade/master

Add operator-ket and operator-bra support to super_tensor.
Update to build_preconditioner

build_preconditioner now raises exception when preconditioning fails