docs(forms): add link to Dart sample (#2176)

Contributes to #1598.

Also:
- Trimmed trailing whitespace.
- Fixing user-input (since we don’t need the “Run the” in the link).

public/docs/dart/latest/guide/forms.jade

@@ -1,6 +1,5 @@
 include ../_util-fns
 
-<!-- http://plnkr.co/edit/wg154K -->
 :marked
   We’ve all used a form to log in, submit a help request, place an order, book a flight,
   schedule a meeting, and perform countless other data entry tasks.
@@ -30,6 +29,8 @@ include ../_util-fns
 
   - How to share information across controls with template reference variables
 
+  Run the <live-example></live-example>.
+
 .l-main-section
 :marked
   ## Template-driven forms

public/docs/dart/latest/guide/user-input.jade

@@ -6,7 +6,7 @@ include ../_util-fns
   In this chapter we learn to bind to those events using the Angular
   event binding syntax.
 
-  <live-example>Run the live example</live-example>.
+  Run the <live-example></live-example>.
 
 :marked
   ## Binding to user input events

public/docs/ts/latest/guide/forms.jade

@@ -29,7 +29,7 @@ include ../_util-fns
 
   - use [template reference variables](./template-syntax.html#ref-vars) for sharing information among HTML elements
 
-  <live-example>Live Example</live-example>
+  Run the <live-example></live-example>.
 
 .l-main-section
 :marked

public/docs/ts/latest/guide/user-input.jade

@@ -6,7 +6,7 @@ include ../_util-fns
   In this chapter we learn to bind to those events using the Angular
   event binding syntax.
 
-  <live-example>Run the live example</live-example>.
+  Run the <live-example></live-example>.
 
 :marked
   ## Binding to user input events