Thanks to the discussion in the comments on the blogpost written by Johan Björnfot I could simplify the code a lot and remove the HttpModule.
Version 3.0.0 is now available on the nuget feed.
It's a major version bump since I removed the HttpModule, you will need to remove the ContentApiModule entry in your web.config to make it work.
Remove the following entry
<system.webServer>
<modules>
.....
<add name="ContentApiModule" type="JOS.Epi.ContentApi.ContentApiModule, JOS.Epi.ContentApi" />
....
</modules>
</system.webServer>