Add :regexp validation to Built-in Validators section
Add section to Parameter Validation about optional default values being passed through to validations
refactoring settings
Merge pull request #739 from dspaeth-faber/refactore_settings

Proposal refactore settings to show the scope of a setting
Merge pull request #749 from phallstrom/master

Update README.  Added section for :regexp validation and note about default values.