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 pull request #138 from jdcaballero/master

Spanish Translation
fix wrong form target on clicking 'Switch to selected version' + modal window height
Merge branch 'master' of github.com:benjaoming/django-wiki
#137 place permission logic ONLY in core.permissions and make article.can_read and article.can_write configurable
Do not use kwargs for permission methods
Do not use kwargs for permission methods
Do not use kwargs for permission methods
Added recursion test for the current bug in preview.
Revert "Fixed posting data to views.article.Preview"

This reverts commit df27e510326ad9e0a9618f27fa93af072d4f9a5c due to broken Preview.
The previous test can pass now.
Merge pull request #139 from hynekcer/master

Fixed broken Preview (displaying the old article content)
pull #139 - form data from args or kwargs
pull #139 - form data from args or kwargs
Merge branch 'master' of github.com:benjaoming/django-wiki
pull #139 - form data from args or kwargs
French translation - changed msg id (att. pull #138)
#140 - Markdown 2.2/2.3 API change - do not rely on markdown.extensions.headerid.unique
Fixed RuntimeWarning by replacing naive datetime by utc