Write integration tests for data-processing modules

We discussed in Brussels that we'll need at least integration tests for metrics-web in order to make code changes like the Java 8 Date/Time API update.

I started working on this. Here's what I did:

• Pick a small set of descriptors as test data that are sufficient to produce at least something as .csv files.
• Write a script that runs all data-processing modules.
• Run the script once to get output that we would expect from future test runs.

The result is too big (IMHO) to add to the Git repository. That's why I uploaded it here:

https://people.torproject.org/~karsten/volatile/metrics-web-integ-tests.tar

shasum -a 256 metrics-web-integ-tests.tar 
728c4e4ee184f2260cd30286f2925aa627d7b3d572a236b646021cc1b461de10  metrics-web-integ-tests.tar

It would be great if somebody else besides me tries this out and verifies that their run produces the same output.

A next good step after that would be to talk about where/how to put this under version control. If that's impossible, we might be able to reduce the test data size a bit more, but maybe not as substantial as we'd want.

Oh, and we could probably fetch libs from Debian rather than shipping them. I didn't bother for now.