Ensure hadoop 1.0 job history files can be processed on 2.0 cluster

[vrushalic]

The work that has gone into refactoring the code and enhancing hraven has been towards ensuring hraven can run on any hadoop version and process any version of job history files.

The earlier related pull request (https://github.com/twitter/hraven/pull/18) ensured that we can process 2.0 job history files on hadoop 1 as well as hadoop 2 clusters

We still need to ascertain that 1.0 job history files can be successfully processed on a hadoop 2.0 cluster. Opening jira to track those changes, if any.