Merge pull request #1720 from astrofrog/fix-custom-init

Fix bug in custom_model_1d
Merge pull request #1734 from astrofrog/fix-mexican-hat-parameter-name

Update Mexican hat model parameter name in docstring
Merge pull request #1491 from astrofrog/fix-docstrings

Fix syntax in docstrings
Initial refactoring on modeling index page
Add a Trapezoid fit to the 1D example
Added sentence describing the fitting