Removing Helpers namespace to standardize on Helper

[ryndaniels]

It turned out that we had two namespaces for helpers - Helper and Helpers. The helpers themselves all use Helper, but other formatters and helpers were using Helpers. Not only is this confusing, but it's inconsistent with how the Formatter and Message namespaces are used. This commit changes this to properly reference Helper, and adds an example of a test case that might have caught this.

[aemcknig]

This looks good and appears to fix the issues that we were seeing! Good catch. 🌷 🐘

[RyanFrantz]

Thanks for tidying up the namespace @kdaniels!