Rename checkbox_style to boolean_style to make it more generic

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

@@ -121,7 +121,7 @@ SimpleForm.setup do |config|
   # Define the way to render checkboxes with labels. Defaults to :inline.
   #   :inline => input + label
   #   :nested => label > input
-  # config.checkbox_style = :inline
+  # config.boolean_style = :inline
 
   # You can define the class to use on all forms. Default is simple_form.
   # config.form_class = :simple_form

lib/simple_form.rb

@@ -64,8 +64,8 @@ module SimpleForm
   # Define the way to render checkboxes with labels. Defaults to :inline.
   #   :inline => input + label
   #   :nested => label > input
-  mattr_accessor :checkbox_style
-  @@checkbox_style = :inline
+  mattr_accessor :boolean_style
+  @@boolean_style = :inline
 
   # You can define the class to use on all forms. Default is simple_form.
   mattr_accessor :form_class

lib/simple_form/inputs/boolean_input.rb

@@ -18,7 +18,7 @@ module SimpleForm
       private
 
       def nested_style?
-        options[:checkbox_style] || SimpleForm.checkbox_style == :nested
+        options[:boolean_style] || SimpleForm.boolean_style == :nested
       end
 
       # Booleans are not required by default because in most of the cases

test/inputs/boolean_input_test.rb

@@ -14,28 +14,28 @@ class BooleanInputTest < ActionView::TestCase
     assert_no_select 'label'
   end
 
-  test 'input uses inline checkbox style by default' do
+  test 'input uses inline boolean style by default' do
     with_input_for @user, :active, :boolean
     assert_select 'input.boolean + label.boolean.optional'
     assert_no_select 'label > input'
   end
 
-  test 'input allows changing default checkbox style config to nested, generating a default label' do
-    swap SimpleForm, :checkbox_style => :nested do
+  test 'input allows changing default boolean style config to nested, generating a default label' do
+    swap SimpleForm, :boolean_style => :nested do
       with_input_for @user, :active, :boolean
       assert_select 'label > input.boolean'
       assert_no_select 'label.boolean'
     end
   end
 
-  test 'input accepts changing checkbox style through given options' do
-    with_input_for @user, :active, :boolean, :checkbox_style => :nested
+  test 'input accepts changing boolean style through given options' do
+    with_input_for @user, :active, :boolean, :boolean_style => :nested
     assert_select 'label > input.boolean'
     assert_no_select 'label.boolean'
   end
 
   test 'input with nested style allows disabling label' do
-    swap SimpleForm, :checkbox_style => :nested do
+    swap SimpleForm, :boolean_style => :nested do
       with_input_for @user, :active, :boolean, :label => false
       assert_select 'input.boolean'
       assert_no_select 'label'