Fix Rails autoloading for Stratify plugins

Customize inflections so that Rails can properly auto-load
Stratify::GitHub and Stratify::ITunes.
Auto-reload Stratify components in lib dir

Use #require_dependency instead of #require so that Rails will
automatically reload during development. Rapid iteration FTW!
Reduce explicit requires, in favor of auto-loading

Rails auto-loading will find the various activity types when they're
needed.

We still need to explicitly load each collector, so that all collectors
get registered, so that they're available in the UI for creating new
collector instances.