chore(addon/components/paper-checkbox): alphabetise attributes.

Author: matthewhartstonge

addon/components/paper-checkbox.hbs

@@ -7,11 +7,11 @@
     {{if @primary " md-primary"}}
     {{if this.focused " md-focused"}}
     {{@class}}'
-  aria-label={{@ariaLabel}}
   aria-checked={{this.ariaChecked}}
+  aria-label={{@ariaLabel}}
   aria-labelledby={{this.labelId}}
-  role='checkbox'
   disabled={{this.disabled}}
+  role='checkbox'
   tabindex={{if this.disabled '-1' '0'}}
   {{did-insert this.didInsertNode}}
   {{will-destroy this.willDestroyNode}}