Merge pull request angular-ui#3275 from jodytate/patch-1

"it" to "it's"

Author: karianna

src/tooltip/docs/readme.md

@@ -3,7 +3,7 @@ directive supports multiple placements, optional transition animation, and more.
 
 There are two versions of the tooltip: `tooltip` and `tooltip-html-unsafe`. The
 former takes text only and will escape any HTML provided. The latter takes
-whatever HTML is provided and displays it in a tooltip; it called "unsafe"
+whatever HTML is provided and displays it in a tooltip; it's called "unsafe"
 because the HTML is not sanitized. *The user is responsible for ensuring the
 content is safe to put into the DOM!*