Deprecate the `eager_load_paths` configuration

Since the default in Rails 4.0 is to run in 'threadsafe' mode we need
to eager load all of the paths in `autoload_paths` so we alias
`eager_load_paths` to it. This may have unintended consequences if
you have added 'lib' to `autoload_paths` such as loading unneeded
code or code intended only for development and/or test environments.
If this applies to your application you should thoroughly check what
is being eager loaded.