fix a js bug with the link field type

when the link dialog was closed with the `esc` button, it would make a js error because `wpLink.textarea` was undefined

the fix is to define it when creating the wpLink object
examples file update

remove all support from the test post type except for titles, makes for more thorough testing when looking at special fields like the `link` field type that may not work otherwise in some cases.

ref #44
properly enqueue resources for the `link` field

* fix improper enqueueing + missing enqueueing of resources for the `link` field type
* if there is no editor on the current post/page, then the `wplink` div will be missing from the page, so we must display the dialog if no editor is present

ref #29