added variance passing with signal inav and isig views
Automatic style corrections courtesy of autopep8
Merge branch 'master' of https://github.com/hyperspy/hyperspy into signal_variance_inav

Conflicts:
	hyperspy/signal.py
Automatic style corrections courtesy of autopep8
fixed to pass varience as required with new metadata structure
Automatic style corrections courtesy of autopep8
removed unnecesarry commented lines
added tests
Automatic style corrections courtesy of autopep8
Merge branch 'master' of https://github.com/hyperspy/hyperspy into signal_variance_inav
fixed behave when variance is a float
fixed to behave when variance is a float
removed unnecessary variance assignment
Merge pull request #203 from to266/signal_variance_inav

Signal variance inav