exclude errors that originate from a local origin

Toggle this boolean and the HTTP module will not send errors to
RayGun.io if the request originated from a local origin. ie. A way to
prevent local debug/development from notifying Raygun without having to
resort to Web.config transforms.

    <RaygunSettings apikey="YOUR_APP_API_KEY" excludeErrorsFromLocal=true />
Merge pull request #131 from ghuntley/master

exclude errors that originate from a local origin