added md5

Oracle Java downloads now use Md5s. The cookbook code supports that. Unfortunately:
https://github.com/socrata/java/blob/master/resources/ark.rb#L34 --
the variable is still checksum, yet in

https://github.com/socrata/java/blob/master/providers/ark.rb#L52 it
makes reference to an md5 variable.

Because it was crashing my cookbooks last night, I made a quick fix. I did a fork and fix here and now my code is using it. It was quick and dirty and I realize I could have done things differently, but it works and has been tested programmatically in the field with several machines.