docs(dateFilter): add example of string literals in format string

Also changes the wording to include the word "escaped" and "escape", which may help users find the
information they're looking for via searching. (ﾉ◕ヮ◕)ﾉ*:･ﾟ✧

Closes angular#8770

Author: dennishall1

src/ng/filter/filters.js

@@ -352,8 +352,8 @@ var DATE_FORMATS_SPLIT = /((?:[^yMdHhmsaZEw']+)|(?:'(?:[^']|'')*')|(?:E+|y+|M+|d
  *   * `'mediumTime'`: equivalent to `'h:mm:ss a'` for en_US locale (e.g. 12:05:08 pm)
  *   * `'shortTime'`: equivalent to `'h:mm a'` for en_US locale (e.g. 12:05 pm)
  *
- *   `format` string can contain literal values. These need to be quoted with single quotes (e.g.
- *   `"h 'in the morning'"`). In order to output single quote, use two single quotes in a sequence
+ *   `format` string can contain literal values. These need to be escaped by surrounding with single quotes (e.g.
+ *   `"h 'in the morning'"`). In order to output a single quote, escape it - i.e., two single quotes in a sequence
  *   (e.g. `"h 'o''clock'"`).
  *
  * @param {(Date|number|string)} date Date to format either as Date object, milliseconds (string or
@@ -373,6 +373,8 @@ var DATE_FORMATS_SPLIT = /((?:[^yMdHhmsaZEw']+)|(?:'(?:[^']|'')*')|(?:E+|y+|M+|d
           <span>{{1288323623006 | date:'yyyy-MM-dd HH:mm:ss Z'}}</span><br>
        <span ng-non-bindable>{{1288323623006 | date:'MM/dd/yyyy @ h:mma'}}</span>:
           <span>{{'1288323623006' | date:'MM/dd/yyyy @ h:mma'}}</span><br>
+       <span ng-non-bindable>{{1288323623006 | date:"MM/dd/yyyy 'at' h:mma"}}</span>:
+          <span>{{'1288323623006' | date:"MM/dd/yyyy 'at' h:mma"}}</span><br>
      </file>
      <file name="protractor.js" type="protractor">
        it('should format date', function() {
@@ -382,6 +384,8 @@ var DATE_FORMATS_SPLIT = /((?:[^yMdHhmsaZEw']+)|(?:'(?:[^']|'')*')|(?:E+|y+|M+|d
             toMatch(/2010\-10\-2\d \d{2}:\d{2}:\d{2} (\-|\+)?\d{4}/);
          expect(element(by.binding("'1288323623006' | date:'MM/dd/yyyy @ h:mma'")).getText()).
             toMatch(/10\/2\d\/2010 @ \d{1,2}:\d{2}(AM|PM)/);
+         expect(element(by.binding("'1288323623006' | date:\"MM/dd/yyyy 'at' h:mma\"")).getText()).
+            toMatch(/10\/2\d\/2010 at \d{1,2}:\d{2}(AM|PM)/);
        });
      </file>
    </example>