fix #12: Allow writer to specify an identifier to a given title

[marmotz]

Source

=title1
=title2=
=title3=newtitle
=title4\=nonewtitle
=title5=new title

Generated

<h1 id="title1">title1</h1>
<h1 id="title2">title2</h1>
<h1 id="newtitle">title3</h1>
<h1 id="title4-nonewtitle">title4=nonewtitle</h1>
<h1 id="new-title">title5</h1>

[Amaury]

Thank you. In fact, I'll refuse your pull request (first one!), just because I rewrote the Title.php file in a simpler manner. I kept your modifications in Config.php.

[marmotz]

ok :)