New AddNoise interface

Simple way to add gaussian (signal) and rayleigh (background) noise
to images
Merge branch 'master' into enh/NewAddNoiseInterface
fix: remove old minified d3. replace with both d3 and minified d3 closes #869
add: new sankey output
Merge branch 'master' into enh/NewAddNoiseInterface

Conflicts:
	nipype/algorithms/misc.py
Fixed AddNoise interface
fix:computation of noise in AddNoise
enh:new feature, rician distributed noise
Merge branch 'master' into enh/NewAddNoiseInterface

Conflicts:
	nipype/algorithms/misc.py
replaced str with basestring in instance checks to support unicode strings
Added input options to dcm2nii
Dcm2nii and related tests
Added whitespaces
Removed unnecessary positional parameters as well as args argument
Remove d3.min.js dependency
Merge branch 'pr/870'

Conflicts:
	nipype/pipeline/engine.py
Merge remote-tracking branch 'origin/pr/923'
Mention AddNoise in the changelog
added external package: 'six'
switched to six.string_types for string type checks