update simpleform configs for 3.1 & bootstrap 3

updated with the generator:
rails generate simple_form:install --bootstrap
fix signup form validation errors - closes #70
fix 'remember me' checkbox alignment
fix new sit datepicker alignment
fix label width in new message form
Merge pull request #182 from chrisdambrosio/simple_form

Update Simple Form Config / Fix Sign-up Validation. Fixes #70