add SimpleForm.default_wrapper

lib/generators/simple_form/templates/config/initializers/simple_form.rb.tt

@@ -49,6 +49,8 @@ SimpleForm.setup do |config|
   # Check the Bootstrap docs (http://twitter.github.com/bootstrap)
   # to learn about the different styles for forms and inputs,
   # buttons and other elements.
+  config.default_wrapper :bootstrap
+
   config.wrappers :bootstrap, :tag => 'fieldset', :class => 'control-group', :error_class => 'error' do |b|
     b.use :placeholder
     b.use :label, :class => 'control-label'

lib/simple_form.rb

@@ -113,6 +113,9 @@ module SimpleForm
   @@button_class = 'button'
 
   ## WRAPPER CONFIGURATION
+  # The default wrapper to be used by the FormBuilder.
+  mattr_accessor :default_wrapper
+  @@default_wrapper = :default
   @@wrappers = {}
 
   # Retrieves a given wrapper

lib/simple_form/form_builder.rb

@@ -32,7 +32,7 @@ module SimpleForm
     def initialize(*) #:nodoc:
       super
       @defaults = options[:defaults]
-      @wrapper  = SimpleForm.wrapper(options[:wrapper] || :default)
+      @wrapper  = SimpleForm.wrapper(options[:wrapper] || SimpleForm.default_wrapper)
     end
 
     # Basic input helper, combines all components in the stack to generate

test/generators/simple_form_generator_test.rb

@@ -17,7 +17,7 @@ class SimpleFormGeneratorTest < Rails::Generators::TestCase
 
   test 'generates the simple_form initializer with the bootstrap wrappers' do
     run_generator %w(--bootstrap)
-    assert_file 'config/initializers/simple_form.rb', /config\.wrappers :bootstrap/
+    assert_file 'config/initializers/simple_form.rb', /config\.wrappers :bootstrap/, /config\.default_wrapper :bootstrap/
   end
 
   %W(erb haml slim).each do |engine|