Fix intermittent wiki_options errors
Fix intermittent wiki_options errors

Changed to resolve intermittent errors where I'd see the following in my logs:

```text
ERROR -- : app error: undefined method `wiki_options' for Precious::App:Class (NoMethodError)
ERROR -- : /home/gollum/production/releases/20141229-172128/vendor/bundle/ruby/2.0.0/gems/gollum-3.1.1.1anchor4/lib/gollum/editing_auth.rb:10:in `call'
ERROR -- : /home/gollum/production/releases/20141229-172128/vendor/bundle/ruby/2.0.0/gems/rack-protection-1.5.3/lib/rack/protection/xss_header.rb:18:in `call'
...
```

I suspect this is the case for Sinatra applications that host instances of Gollum using its `map` feature, as this reflects the production setup we're using it in. Calling @app.settings.wiki_options uses the app instance that gets passed into Precious::EditingAuth, thereby ensuring that we're getting a Gollum instance all the time.
n-st/gollum,rgroux/gollum,gollum/gollum,FreifunkMD/gollum,FreifunkMD/gollum,guke001/gollum,Komodo/kollum,mchill/gollum,ngyuki/gollum,jinhu/gollum,willhurley004/gollum_1916,guke001/gollum,yuanmeibin/gollum,doordash/gollum,webwlsong/gollum,bpieck/gollum,jhominal/gollum,manueldeval/gollum,paddingme/gollum,jinhu/gollum,cheenwe/gollum,mhs/gollum,doordash/gollum,diguage/gollum,kissthink/gollum,diguage/gollum,paddingme/gollum,gollum/gollum,doordash/gollum,guke001/gollum,jhominal/gollum,assilzm/gollum,ProgramFan/gollum,manueldeval/gollum,yuanmeibin/gollum,n-st/gollum,dometto/gollum,n-st/gollum,mhs/gollum,n-st/gollum,rgroux/gollum,manueldeval/gollum,repotag/gollum,youprofit/gollum,obbectim/gollum,blabtonic/burning-wiki,kissthink/gollum,blabtonic/burning-wiki,repotag/gollum,webwlsong/gollum,obbectim/gollum,sunnyone/gollum,gollum/gollum,bpieck/gollum,repotag/gollum,youprofit/gollum,gollum/gollum,ProgramFan/gollum,rgroux/gollum,tricker/gollum,manueldeval/gollum,apfohl/gollum,FreifunkMD/gollum,dometto/gollum,assilzm/gollum,jhominal/gollum,arr2036/gollum,jinhu/gollum,rgroux/gollum,tricker/gollum,sunnyone/gollum,mhs/gollum,bpieck/gollum,Komodo/kollum,jinhu/gollum,tricker/gollum,bpieck/gollum,guke001/gollum,webwlsong/gollum,ngyuki/gollum,cheenwe/gollum,andrehjr/gollum,arr2036/gollum,foursquare/gollum-OSS,obbectim/gollum,mchill/gollum,gollum/gollum,ngyuki/gollum,Komodo/kollum,andrehjr/gollum,apfohl/gollum,diguage/gollum,paddingme/gollum,mhs/gollum,kissthink/gollum,willhurley004/gollum_1916,arr2036/gollum,foursquare/gollum-OSS,mchill/gollum,kwoods/gollum,andrehjr/gollum,sunnyone/gollum,repotag/gollum,cheenwe/gollum,willhurley004/gollum_1916,webwlsong/gollum,sunnyone/gollum,assilzm/gollum,blabtonic/burning-wiki,Komodo/kollum,willhurley004/gollum_1916,kwoods/gollum,kwoods/gollum,dometto/gollum,jhominal/gollum,FreifunkMD/gollum,assilzm/gollum,rgroux/gollum,blabtonic/burning-wiki,apfohl/gollum,repotag/gollum,foursquare/gollum-OSS,mchill/gollum,yuanmeibin/gollum,paddingme/gollum,arr2036/gollum,cheenwe/gollum,doordash/gollum,foursquare/gollum-OSS,diguage/gollum,obbectim/gollum,dometto/gollum,tricker/gollum,kwoods/gollum,ngyuki/gollum,ProgramFan/gollum,andrehjr/gollum,youprofit/gollum,kissthink/gollum,youprofit/gollum,ProgramFan/gollum,yuanmeibin/gollum