Added a concern to configure Agents via HTML forms

Validate input forms based on a callback
Offer valid options for parameters
FormConfigurable improvements

Made the BasecampAgent form configurable
Added specs
Added guard-livereload and guard-rspec
Custom values can be entered for `completable` attributes
Fixes the specs
Added spec for the FormConfigurableAgentPresenter
FormCompletable: Show error message if the completable ajax call failed
Allow manual input for boolean and array form-configurable types
Fixes the specs
Added format to the HipchatAgent default options
Merge pull request #499 from dsander/form-configurable

Configure agents via HTML forms rather then JSON