fix "Template Not Found" error

This fixes an error in which GET requests to /channels/<channel_id>/status.(format) fail with a "Template Not Found" error for JSON, CSV, and XML formats.

The status controller was previously requesting templates from ./app/views/status/feed/index and /app/views/application/feed/index, instead of ./app/views/feed/index.  I have never worked in Ruby or with Rails before, so this might be caused by a configuration issue on my end, or there may be a different/preferred syntax for the 'render' calls, but this seems to do the trick.

In order to re-use the feed view with the status controller (as I believe was the intention) , the variable names in the status controller have been updated to match those in the feed controller and the feed templates.

With this patch, the behavior and output of status requests are now the same as api.thingspeak.com.