Allow single element array as POST params. Fixes #152.

We could be receiving an array as POST parameters. In this cases we cannot merge an array into the rest of the hash params. Only in case that the array has only one element we could try to merge it.
While get route params, return empty Hash unless Rails is defined.
Allow hashes, arrays or other values as raw POST body.

* If the parsed body is a Hash we just return the hash.
* If the parsed body is an Array we return { 'body.multi' => array }
* If the parsed body is other value we retur { 'body.value' => value }
Merge pull request #153 from rollbar/fix-array-body-parsing

Allow hashes, arrays or other values as POST body