Invalid function: te/delete-to

I have installed `tagedit` through `package.el` and whenever I type in
a singleton html tag the error "Invalid function: te/delete-to" is
signaled. This happens to me, for example, when typing an `input`
element.

This error disappears if I just evaluate the code in `tagedit.el`
using `eval-buffer`.

The accompanying commit fixes this problem for me without requiring me
to manually evaluate the code.

The easiest way that I can reproduce this is by having tagedit
installed with package.el, using `emacs -Q` and then evaluating:

```lisp
(package-initialize)
(require 'tagedit)
(add-hook 'html-mode-hook 'tagedit-mode)
(add-hook 'tagedit-mode-hook 'tagedit-add-experimental-features)
```

And then typing `<input` into an html buffer, which produces

```html
<input></inpu>
```

And the error in the echo area.