Make plugin work properly in Chrome

If you place the jquery.balancetext.js `<script>` tag in the `<head>`
element, in Chrome it might not fire on initial page load (only after
the browser is resized). This fixes that.

Also simplify README example, dropping the placement requirement for
`<style>` and `<script>` tags. You can put them anywhere.

Also move `<script>` tags to the `<head>` element in sample/test files.

Fixes #29.