also get a proper git version for not annotated tags
Merge pull request #1 from FreifunkMD/fix-makefile

also get a proper git version for not annotated tags
use calloc instead of malloc+memset
alfred.h: fix indentation
disable GZip decompression by default

Transparent GZip decompression has been disabled by default. To enable,
use the -z argument, e.g.:

    alfred-json -zr 158
output version on -h
mention [-z] in usage