Fix handling of 'size' attribute on numeric inputs

Validators complain that SimpleForm's numeric elements have a `size`
attribute. According to the [spec][1], `input` elements with a `type`
of `number` must not specify a `size`. This change removes the `size`
option, and updates an existing unit test to guard against regressions.

Users may still provide a `size` option manually, though it may produce
invalid markup in certain situations.

[1]: http://www.whatwg.org/specs/web-apps/current-work/multipage/number-state.html#number-state

lib/simple_form/inputs/numeric_input.rb

@@ -3,7 +3,7 @@ module SimpleForm
     class NumericInput < Base
       def input
         input_html_options[:type] ||= "number" if SimpleForm.html5
-        input_html_options[:size] ||= SimpleForm.default_input_size
+        input_html_options[:size] ||= nil
         input_html_options[:step] ||= integer? ? 1 : "any" if SimpleForm.html5
         infer_attributes_from_validations! if SimpleForm.html5
         @builder.text_field(attribute_name, input_html_options)

test/inputs_test.rb

@@ -141,9 +141,9 @@ class InputTest < ActionView::TestCase
     assert_select "input#user_password.password[type=password][name='user[password]']"
   end
 
-  test 'input should use default text size for decimal attributes' do
+  test 'input should not use size attribute for decimal attributes' do
     with_input_for @user, :credit_limit, :decimal
-    assert_select 'input.decimal[size=50]'
+    assert_no_select 'input.decimal[size]'
   end
 
   test 'input should get maxlength from column definition for string attributes' do