[ng] template-syntax: use ngSwitchWhen (#328)

TS updated its syntax to `ngSwitchCase` and I failed to notice the
change in the prose. AngularDart is still using `ngSwitchWhen` — this
PR reverts the change in the prose.

Fixes #288

Author: chalin

src/angular/guide/template-syntax.jade

@@ -1151,14 +1151,14 @@ figure.image-display
 :marked
   Three collaborating directives are at work here:
   1. `ngSwitch`: bound to an expression that returns the switch value
-  1. `ngSwitchCase`: bound to an expression returning a match value
+  1. `ngSwitchWhen`: bound to an expression returning a match value
   1. `ngSwitchDefault`: a marker attribute on the default element
 
 .alert.is-critical
   :marked
     **Do *not*** put the asterisk (`*`) in front of `ngSwitch`. Use the property binding instead.
 
-    **Do** put the asterisk (`*`) in front of `ngSwitchCase` and `ngSwitchDefault`.
+    **Do** put the asterisk (`*`) in front of `ngSwitchWhen` and `ngSwitchDefault`.
     For more information, see [\* and <template>](#star-template).
 
 <a id="ngFor"></a>
@@ -1293,16 +1293,16 @@ figure.image-display
 :marked
   ### Expanding `*ngSwitch`
   A similar transformation applies to `*ngSwitch`. We can unfold the syntax ourselves.
-  Here's an example, first with `*ngSwitchCase` and `*ngSwitchDefault` and then again with `<template>` tags:
+  Here's an example, first with `*ngSwitchWhen` and `*ngSwitchDefault` and then again with `<template>` tags:
 +makeExample('template-syntax/ts/app/app.component.html', 'NgSwitch-expanded')(format=".")
 :marked
-  The `*ngSwitchCase` and `*ngSwitchDefault` expand in exactly the same manner as `*ngIf`,
+  The `*ngSwitchWhen` and `*ngSwitchDefault` expand in exactly the same manner as `*ngIf`,
   wrapping their former elements in `<template>` tags.
 
   Now we can see why the `ngSwitch` itself is not prefixed with an asterisk (*).
   It does not define content. It's job is to control a collection of templates.
 
-  In this case, it governs two sets of `ngSwitchCase` and `NgSwitchDefault` directives.
+  In this case, it governs two sets of `ngSwitchWhen` and `NgSwitchDefault` directives.
   We should expect it to display the values of the selected template twice,
   once for the (*) prefixed version and once for the expanded template version.
   That's exactly what we see in this example: