Use Java 7's diamond operator wherever possible
I'll shortly attach three branches that use Java 7's diamond operator wherever possible in ExoneraTor, CollecTor, and Metrics. We already did this in Onionoo and metrics-lib, so that there aren't any metrics code bases left where we'd need to do this.
Note that I didn't touch any nearby code. There's lots to be cleaned up. But let's do one thing at a time.
This was on my local TODO list for a while, and it seemed easiest to just make these changes and be able to cross out yet another item.