Add jsonpath gem as a dependency
Update code to accept a jsonpath instead of a Proc
Associated tests for new jsonpath work (this was done TDD but I ended up committing the code first and not the tests)
Fix up formatting/syntax OCD stuff
Finish remaining tests and refactor code
Discovered bug when integrating with renderer application...

- The JsonPath gem only works with a true JSON data string
- We were pre-parsing the data *then* passing it onto Sequencer
- Now we on parse the JSON when we're ready to write to S3
Updated tests & code to fix a bug
Refactor method name
Merge pull request #30 from BBC-News/remove-procs

Remove Procs and utilise jsonpath lookups