Initial Implementation of Search using Haystack

This is an initial implementation although functional. Currently the template for search is duplicated taking into account the use of search query sets by haystack instead of query sets. If we could detect this inside the template this could be avoided. The parameter name query was changed to q for interoperability with Haystack. This parameter is hard coded in haystack and interacts between class view and form.

Bug: Currently the search shows articles that the user cant read. This can be corrected in the override to the method __call__. An efficient way of doing it must be used.
Another option can be rewriting the form, since in Haystack the search is actually done by the form!. SearchForm.form returns a search query set captured by __call__ in the view class that then is used to create the response by create_response inside the view.
Paginator used to show the number of results
Permissions bare implementation
Merge remote-tracking branch 'jdcaballero/haystack-search' into haystack-search

Starting haystack-search implementation based on the work of jdcaballero
Some minor cleanup and same redirect behaviour on anonymous access
Haystack 2.0 broke some stuff (site did not exist). This is fixed now. Furthermore we can use the highlighter by haystack. It does some stuff nicer than django-wikis
Minor fix
Merge pull request #1 from TomLottermann/haystack-search

Haystack search
Merge branch 'haystack-search' of git://github.com/jdcaballero/django-wiki into jdcaballero-haystack-search