chore(tooltip): add note on wrapping in a tag

- Add documentation to tooltip and popover about usage of `*-template` and the template needing to be wrapped in a tag

Closes #3555
Closes #4101

Author: wesleycho

src/popover/docs/readme.md

@@ -11,7 +11,7 @@ There are two versions of the popover: `popover` and `popover-template`:
 - `popover-html` takes an expression that evaluates to an html string. *The user is responsible for ensuring the
   content is safe to put into the DOM!*
 - `popover-template` takes text that specifies the location of a template to
-  use for the popover body.
+  use for the popover body. Note that this needs to be wrapped in a tag.
 
 The popover directives provides several optional attributes to control how it
 will display:

src/tooltip/docs/readme.md

@@ -6,7 +6,7 @@ There are three versions of the tooltip: `tooltip`, `tooltip-template`, and
 
 - `tooltip` takes text only and will escape any HTML provided.
 - `tooltip-template` takes text that specifies the location of a template to
-  use for the tooltip.
+  use for the tooltip. Note that this needs to be wrapped in a tag.
 - `tooltip-html` takes
   whatever HTML is provided and displays it in a tooltip; *The user is responsible for ensuring the
   content is safe to put into the DOM!*