Fix for Issue #17 (take 2)

* Structural Change - now its a "package" that can contain multiple files
   This may be extreme, but it is probably better in the end?
* Updated spec to have a / (which may not have been required)
* Moved "version" from config to src/_version.py
   * Modified setup.py, newrhelic.py to read version from new file
* Moved the following from the config to self variables
   * name
   * guid
   * api_url
* Changed "duration" to "interval" which more closely defines what it is
   * Future change: duration needs to be tracked separately in the event
      of a failure to post data.