Added the set_delimiters() function

If there is need to change the delimiters, just use $this->presenter->set_delimiters('{', '}').

I made this for standardize the HTML markup of presenter, equal to the [parser library of CI] (http://ellislab.com/codeigniter/user-guide/libraries/parser.html).

<p>Listing: Product #name# costs #price# </p>

With: $this->presenter->set_delimiters('{', '}');

I change the string delimiter, # # to { }.
<p>Listing: Product {name} costs {price} </p>