Adds HelperError rescue class

[nicholaskuechler]

The missing HelperError rescue class obfuscates the real problem or error should one arise in the web app.

For example, with the HelperError rescue class in place I can see this error:

Redis::CannotConnectError at /
Error connecting to Redis on 11.22.33.44:6379 (ECONNREFUSED)

But without the class I only see:

NameError at /
uninitialized constant Oculusweb::HelperError

[jonlives]

Thanks for this, good catch - no idea how I missed that :p