Replace deprecated param_dim with n_models
Update detect_sources docs
Merge pull request #109 from larrybradley/model_update

Replace deprecated param_dim with n_models
Simplify docs in scale_img
Add segment_photometry
Update segment_photometry docs
Allow label subset for segment_photometry
Change index to labels and make flux nan for invalid labels
Implement error, gain, and mask options in segment_photometry