use git describe instead of hard-coded version number in build scripts

docker-build-centos.sh

@@ -1,11 +1,11 @@
 #!/bin/bash
 
-VERSION=0.3
-
 OUTPUT_DIR=$PWD
 
 SOURCE_DIR=$(readlink -f $(dirname ${BASH_SOURCE[0]}))
 
+VERSION=$(cd "$SOURCE_DIR" && git describe --tags --abbrev=8 --dirty)
+
 docker run --rm -i -v $SOURCE_DIR:/root/rpmbuild/SOURCES/laminar-$VERSION:ro -v $OUTPUT_DIR:/output centos bash -xe <<EOS
 
 yum -y install epel-release

docker-build-debian.sh

@@ -1,11 +1,11 @@
 #!/bin/bash
 
-VERSION=0.3
-
 OUTPUT_DIR=$PWD
 
 SOURCE_DIR=$(readlink -f $(dirname ${BASH_SOURCE[0]}))
 
+VERSION=$(cd "$SOURCE_DIR" && git describe --tags --abbrev=8 --dirty)
+
 docker run --rm -i -v $SOURCE_DIR:/laminar:ro -v $OUTPUT_DIR:/output debian:stable bash -xe <<EOS
 
 apt-get update