Adding corpus of JSON/XML Data for Benchmarking Compression in REST interfaces

Tatu,
I forked this to add a new corpus to  for benchmarking compression in REST APIs. This corpus included JSON/XML files taken from a variety of public REST APIs (the sources are included here along with shellscriptto re-fetch new versions of the data).   I also added tests using the corpus, and a basic shell script for converting a corpus to test files.  

I'd like to offer this back for merging into the main project, because it seems like others might have similar use cases.   Please let me know if there are changes desired to bring this into fitting with the overall project. 

Thanks,
Sam Van Oort

PS: I think we share some common history around the H2 database, many moons ago, no?