kiji-poms: POM-35 Assembly plugin creates bad permissions in archives.

Adds some default decimal permissions to assembly plugin.
I don't like this change, but it seems to fix
https://jira.codehaus.org/browse/MASSEMBLY-449 issues.

issue: https://jira.kiji.org/browse/POM-35
review: https://review.kiji.org/r/1886
commit: https://github.com/kijiproject/kiji-poms/commit/48e1912e9b7ac5698e9d4513d210d5b40ffa9653