Add support of text files by setting a default title.

[nicofrand]

If you try to import the text on this page : http://pastebin.com/raw.php?i=MnbZJC6h,
which does not have a title specified since it is just a text file, Poche will fail to add a title and therefore, the user will not be able to open it.

Poche should set a default title (event "Untitled" would be fine) so that the content is fully readable again.