Build.sh: exit with an error if MiniMaven failed

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Build.sh: make sure that scijava-common is installed

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Switch to a -SNAPSHOT version of MiniMaven temporarily

Sonatype has problems, so our deployment of MiniMaven 2.1.1 timed out :-(

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>