Added zlib and compression as an option to snapshots

Samo Penic

2016-02-15 22721d3dc98cae61db96021c01ee8dc1cbdf462d

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Original written by Dan Kroll in FORTRAN. Code was then largely adapted and commented by Miha Fosnaric-Fosni. Rewritten into C by Samo Penic-Peni, with help of Miha's extensive explanations.