Remove evaluator caching for text section

This pull request removes the the evaluator caching for text section from can.stache which fixes the original issue #1065. Caching was done under the assumption that in a text sub section all expressions contain the same content making a simple template like the following fail:

```html
<h2 class="{{#shown}}foo{{/if}} test {{#shown}}bar{{/shown}}"></h2>
```

The only solution I could find was removing the evaluator caching which does slow down performance for the visual benchmark.