update yaml file
add modelaggregator
ENH: Added ModelAggregator VisTrails module

- Also updated yaml file based on my changes to NSLS2.fitting
resolve conflicts
add modelaggregator
Merge branch 'gaussian_fit' of github.com:licode/VTTools into gaussian_fit
Merge pull request #28 from licode/gaussian_fit

Model Sum and Model Aggregator
MNT: Local merge due to conflicts
Merge pull request #29 from ericdill/model_aggregator

Merging this because the variable names are better.