Fix minor things in <u> documentation

Author: pascalwengerter

docs/components/u.md

@@ -1,33 +1,36 @@
-# matestack core component: Hr
+# matestack core component: U
 
-Show [specs](/spec/usage/components/hr_spec.rb)
+Show [specs](/spec/usage/components/u_spec.rb)
 
-The HTML `<u>` tag implemented in ruby.
+The HTML `<u>` tag implemented in Ruby.
 
 ## Parameters
 
-This component can take 2 optional configuration params.
+This component can take 2 optional configuration params and either yield content or display what gets passed to the `text` configuration param.
 
 #### # id (optional)
 Expects a string with all ids the u should have.
 
 #### # class (optional)
 Expects a string with all classes the u should have.
 
+
 ## Example 1
 Adding an optional id
 
 ```ruby
 div id: "foo", class: "bar" do
-  u id: "u-id"
+  u id: "u-id" do
+    plain 'Example text'
+  end
 end
 ```
 
 returns
 
 ```html
 <div id="foo" class="bar">
-  <u id="u-id">
+  <u id="u-id">Example text</u>
 </div>
 ```
 
@@ -36,14 +39,14 @@ Adding an optional class
 
 ```ruby
 div id: "foo", class: "bar" do
-  u class: "u-class"
+  u class: "u-class", text: 'Example text'
 end
 ```
 
 returns
 
 ```html
 <div id="foo" class="bar">
-  <u class="u-class">
+  <u class="u-class">Example text</u>
 </div>
 ```