Fixing a bug where ajax wouldn't grab whole document in case there was ampersands in link.

The ajax request is being sent to html page hence you should use html as data type. Using xml might break in case there is un-escaped characters such as "<" or "&" in html. In fact it was causing problems when trying to retrieve bibtex data for particular item which included link with an ampersand.

It was mentioned in comments section in website by Tobi:

> Tobi: Hi Martin, 
> 
> it seems like bibtexbrowser cannot handle & (ampersands) in URLs. Entries that contain & confuse > the bibtex-block-script, which displays bibtex information in a new site instead of loading the > block of information just below the entry. I can't seem to find the bug, but hope that you can. 
> 
> Tobi
> (May 27, 2014 - 6:33 pm)

Also I have found some random page which is using bibtexbrowser and you can see the bug here http://www.imp.kiev.ua/~kord/papers/ by clicking on "Strong electron pairing at the iron 3dxz,yz orbitals in hole-doped BaFe2As2 superconductors revealed by angle-resolved photoemission spectroscopy" article's bib anchor.