more specific test for valid, selectable id

@r4j4h, as commented in #800.  Thanks again!

Changelog.md

@@ -1,4 +1,7 @@
-## 2.0.0 alpha 6
+## 2.0.0 beta 1
+ * Merged #800: unselectable ids starting with numbers #789. Thanks Jasmine Hegman!
+ * Interface and features frozen - from this point all fixes will be merged to
+   `master` and `develop`, and all interface changes only merged to `develop`.
 
 ## Starting dc.js Changelog
  * Here we start using git-flow, start a changelog, and start 2015.  Under git-flow,

spec/base-mixin-spec.js

@@ -213,13 +213,9 @@ describe("dc.baseMixin", function () {
                     expect(chart.anchor()).toEqual(anchorDiv);
                 });
 
-                it('should return a numeric string, when anchorName is called', function () {
-                    expect(dc.utils.isNumber(chart.anchorName())).toBeFalsy();
-                    expect(chart.anchorName()).toMatch(/\d+/);
-                });
-
-                it('should return a string that begins with a non-numeric character', function () {
-                    expect(chart.anchorName()).toMatch(/[^\d][\w]*/);
+                it('should return a valid, selectable id', function () {
+                    // see http://stackoverflow.com/questions/70579/what-are-valid-values-for-the-id-attribute-in-html
+                    expect(chart.anchorName()).toMatch(/^[a-zA-Z][a-zA-Z0-9_:.-]*$/);
                 });
 
             });