Pass msg_level and remove duplicated checks

This makes the Study Description page render again.
I was thinking about this and we could subclass render and add those
arguments with those defaults, and then change sitebase.html to no longer
check the global variables to see if those variables are available. Not
sure if this would work.

On (Nov-14-14|10:58), adamrp wrote:
> >              raise HTTPError(404, "Study %s does not exist" % study_id)
> >          else:
> >              check_access(User(self.current_user), study)
> >  
> > -        self.display_template(int(study_id), "")
> > +        self.display_template(study, "", 'info')
> 
> Hmm -- there is no reason that `level` or `message` need to be passed to the call to `render` ([see these lines in sitebase](https://github.com/biocore/qiita/blob/master/qiita_pet/templates/sitebase.html#L23-L36)).  A better fix here would be to redefine `display_template` to have default arguments for those parameters:
> ```python
> def display_template(self, study, msg="", msg_level="", tab_to_display=""):
> ```
> 
> ---
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> https://github.com/biocore/qiita/pull/606/files#r20378125