Add a test for edge case. Remove an unneeded test.
Add a test for edge case. Remove an unneeded test.

In the current master branch, the following code will break the HTML
structure in the text, and will display `1...</b>` unexpectedly:
```
Text::truncate('1 <b>2 345</b>', 6, [
    'exact' => false,
    'html' => true,
    'ellipsis' => '...'
])
```
Now it works fine.

garethellis36/cakephp,ionas/cakephp,ndm2/cakephp,cakephp-fr/cakephp,cakephp/cakephp,garethellis36/cakephp,HavokInspiration/cakephp,elboletaire/cakephp,HavokInspiration/cakephp,dakota/cakephp,elboletaire/cakephp,CVO-Technologies/cakephp,elboletaire/cakephp,cakephp-fr/cakephp,ndm2/cakephp,ADmad/cakephp,ADmad/cakephp,mvdriel/cakephp,berrygoudswaard/cakephp,tenkoma/cakephp,cakephp/cakephp,CVO-Technologies/cakephp,berrygoudswaard/cakephp,mvdriel/cakephp,nrother/cakephp,nrother/cakephp,petteyg/cakephp,thinkingmedia/cakephp,tenkoma/cakephp,CakeDC/cakephp,garethellis36/cakephp,cakephp/cakephp,cakephp-fr/cakephp,CakeDC/cakephp,ndm2/cakephp,ADmad/cakephp,dakota/cakephp,CakeDC/cakephp,cakephp/cakephp,mvdriel/cakephp,ndm2/cakephp,ionas/cakephp,davidyell/cakephp,tenkoma/cakephp,tenkoma/cakephp,thinkingmedia/cakephp,ADmad/cakephp,dakota/cakephp,petteyg/cakephp,davidyell/cakephp,garethellis36/cakephp,davidyell/cakephp,thinkingmedia/cakephp,CakeDC/cakephp,petteyg/cakephp,berrygoudswaard/cakephp,ionas/cakephp,nrother/cakephp,HavokInspiration/cakephp,CVO-Technologies/cakephp,mvdriel/cakephp,dakota/cakephp,petteyg/cakephp